Low-carbohydrate diets for overweight and obesity: a systematic review of the systematic reviews

Guidance to best tools and practices for systematic reviews

Data continue to accumulate indicating that many systematic reviews are methodologically flawed, biased, redundant, or uninformative. Some improvements have occurred in recent years based on empirical methods research and standardization of appraisal tools; however, many authors do not routinely or consistently apply these updated methods. In addition, guideline developers, peer reviewers, and journal editors often disregard current methodological standards. Although extensively acknowledged and explored in the methodological literature, most clinicians seem unaware of these issues and may automatically accept evidence syntheses (and clinical practice guidelines based on their conclusions) as trustworthy. A plethora of methods and tools are recommended for the development and evaluation of evidence syntheses. It is important to understand what these are intended to do (and cannot do) and how they can be utilized. Our objective is to distill this sprawling information into a format that is understandable and readily accessible to authors, peer reviewers, and editors. In doing so, we aim to promote appreciation and understanding of the demanding science of evidence synthesis among stakeholders. We focus on well-documented deficiencies in key components of evidence syntheses to elucidate the rationale for current standards. The constructs underlying the tools developed to assess reporting, risk of bias, and methodological quality of evidence syntheses are distinguished from those involved in determining overall certainty of a body of evidence. Another important distinction is made between those tools used by authors to develop their syntheses as opposed to those used to ultimately judge their work. Exemplar methods and research practices are described, complemented by novel pragmatic strategies to improve evidence syntheses. The latter include preferred terminology and a scheme to characterize types of research evidence. We organize best practice resources in a Concise Guide that can be widely adopted and adapted for routine implementation by authors and journals. Appropriate, informed use of these is encouraged, but we caution against their superficial application and emphasize their endorsement does not substitute for in-depth methodological training. By highlighting best practices with their rationale, we hope this guidance will inspire further evolution of methods and tools that can advance the field.

The effects of the ketogenic diet for the management of type 2 diabetes mellitus: A systematic review and meta-analysis of recent studies

OBJECTIVE

To systematically review the effects of the ketogenic diet on glycaemic control, body weight, cardiovascular risk factors, and liver and kidney function in patients with type 2 diabetes.

METHODS

PubMed, MEDLINE, Embase, Cochrane Library and CINAHL were searched for randomised controlled trials published between 2001 and 2021 that compared the ketogenic diet to a control diet for effects on glycaemic control, body weight, cardiovascular risk factors, liver and renal function markers in adults with type 2 diabetes for >14 days. Meta-analyses using fixed or random effects models were conducted.

RESULTS

Nineteen reports from 11 randomised controlled trials were included. Compared to the control, the ketogenic diet showed no significant difference in changes in glycaemic control or body weight, but greater increases in HDL (standardised mean difference 0.19; 95%CI 0.02-0.37; I2 = 0 %; moderate-quality evidence) and greater reductions in triglycerides (standardised mean difference -0.41; 95%CI -0.64 to -0.18; I2 = 0 %; low-quality evidence).

CONCLUSIONS

The ketogenic diet may improve lipid profiles but showed no additional benefits for glycaemic control or weight loss compared to control diets in type 2 diabetes patients over two years.

A low-carbohydrate diet with different fatty acids' sources in the treatment of obesity: Impact on insulin resistance and adipogenesis

BACKGROUND

The search for nutritional intervention strategies against obesity has grown, highlighting the low-carbohydrate diet model. However, little is known about the impact of the quality of fatty acids consumed in this diet. Thus, we aim to investigate the influence of fatty acid quality on dietary strategy on obesity.

METHODS

Male Swiss mice were diet-induced to obesity. Afterward, mice consume a low-carb diet with different types of fat: saturated, polyunsaturated ω-3, ω-6, and monounsaturated ω-9 fatty acids. Weight gain and food consumption were monitored weekly. An oral glucose tolerance test was performed and blood and tissue samples were collected for analysis of insulin resistance markers. Protein expression of insulin signaling pathway molecules, lipid metabolism, mitochondrial function, macrophage polarization, and cytokine production were analyzed.

RESULTS

The high-fat diet was able to induce obesity and glucose intolerance. The switch to a low-carbohydrate dietary pattern reversed the glucose intolerance, with better results in the ω-3 and ω-9 groups. After the low-carbohydrate diet, groups ω-3 and ω-9 presented improved fasting serum glucose, insulin, and HOMA indexes. The low-carbohydrate diet also increased the activity of insulin pathway proteins such as IR, IRS1, and AKT. Furthermore, the ω-3 diet group showed greater activity of mitochondrial complexes and AMPK signaling pathway proteins. The ω-6 and ω-9 -rich diet induced M2-type macrophage polarization, as well as cytokine production modulation by the low-carbohydrate diet in the ω-3 and ω-9 groups.

CONCLUSIONS

Consuming a low-carbohydrate diet pattern promotes weight loss and improves glucose intolerance in obesity. Also, the quality of lipids has a direct influence, demonstrating that the consumption of ω-3 polyunsaturated and ω-9 monounsaturated lipids can lead to more favorable outcomes for the improvement of glucose intolerance, lipid metabolism, and anti-inflammatory effects.

Popular Diets and Kidney Stones

Popular diets often influence dietary patterns, which have different implications for kidney stone risk. Despite the wide variety of popular diets, some general principles can be gleaned from investigating their potential impact on nephrolithiasis. Plant-based diets, including Dietary Approaches to Stop Hypertension, Mediterranean, flexitarian, and vegetarian diets, may protect against nephrolithiasis when they consist largely of unprocessed plant foods, while carbohydrate-restricted diets (including high-protein diets and the ketogenic diet) may raise kidney stone risk. Patients should be advised to consume a diet rich in whole plants, particularly fruits and vegetables, and minimize their consumption of animal proteins. Accompanying fruits and vegetables that are higher in oxalate content with more water and some dairy intake may also be useful. (We address the oxalate content of fruits and vegetables further below). Calcium consumption is an important component of decreasing the risk of kidney stones, as higher dietary calcium from dairy or nondairy sources is independently associated with lower kidney stone risk. Patients should also be advised to be conscious of fat intake, as fat in the intestinal lumen may complex with calcium and therefore increase urinary oxalate excretion. Finally, patients should avoid consumption of processed foods, which often contain added fructose and high sodium content, two factors that increase kidney stone risk.

Guidance to best tools and practices for systematic reviews

Data continue to accumulate indicating that many systematic reviews are methodologically flawed, biased, redundant, or uninformative. Some improvements have occurred in recent years based on empirical methods research and standardization of appraisal tools; however, many authors do not routinely or consistently apply these updated methods. In addition, guideline developers, peer reviewers, and journal editors often disregard current methodological standards. Although extensively acknowledged and explored in the methodological literature, most clinicians seem unaware of these issues and may automatically accept evidence syntheses (and clinical practice guidelines based on their conclusions) as trustworthy. A plethora of methods and tools are recommended for the development and evaluation of evidence syntheses. It is important to understand what these are intended to do (and cannot do) and how they can be utilized. Our objective is to distill this sprawling information into a format that is understandable and readily accessible to authors, peer reviewers, and editors. In doing so, we aim to promote appreciation and understanding of the demanding science of evidence synthesis among stakeholders. We focus on well-documented deficiencies in key components of evidence syntheses to elucidate the rationale for current standards. The constructs underlying the tools developed to assess reporting, risk of bias, and methodological quality of evidence syntheses are distinguished from those involved in determining overall certainty of a body of evidence. Another important distinction is made between those tools used by authors to develop their syntheses as opposed to those used to ultimately judge their work. Exemplar methods and research practices are described, complemented by novel pragmatic strategies to improve evidence syntheses. The latter include preferred terminology and a scheme to characterize types of research evidence. We organize best practice resources in a Concise Guide that can be widely adopted and adapted for routine implementation by authors and journals. Appropriate, informed use of these is encouraged, but we caution against their superficial application and emphasize their endorsement does not substitute for in-depth methodological training. By highlighting best practices with their rationale, we hope this guidance will inspire further evolution of methods and tools that can advance the field.

Guidance to best tools and practices for systematic reviews

Data continue to accumulate indicating that many systematic reviews are methodologically flawed, biased, redundant, or uninformative. Some improvements have occurred in recent years based on empirical methods research and standardization of appraisal tools; however, many authors do not routinely or consistently apply these updated methods. In addition, guideline developers, peer reviewers, and journal editors often disregard current methodological standards. Although extensively acknowledged and explored in the methodological literature, most clinicians seem unaware of these issues and may automatically accept evidence syntheses (and clinical practice guidelines based on their conclusions) as trustworthy. A plethora of methods and tools are recommended for the development and evaluation of evidence syntheses. It is important to understand what these are intended to do (and cannot do) and how they can be utilized. Our objective is to distill this sprawling information into a format that is understandable and readily accessible to authors, peer reviewers, and editors. In doing so, we aim to promote appreciation and understanding of the demanding science of evidence synthesis among stakeholders. We focus on well-documented deficiencies in key components of evidence syntheses to elucidate the rationale for current standards. The constructs underlying the tools developed to assess reporting, risk of bias, and methodological quality of evidence syntheses are distinguished from those involved in determining overall certainty of a body of evidence. Another important distinction is made between those tools used by authors to develop their syntheses as opposed to those used to ultimately judge their work. Exemplar methods and research practices are described, complemented by novel pragmatic strategies to improve evidence syntheses. The latter include preferred terminology and a scheme to characterize types of research evidence. We organize best practice resources in a Concise Guide that can be widely adopted and adapted for routine implementation by authors and journals. Appropriate, informed use of these is encouraged, but we caution against their superficial application and emphasize their endorsement does not substitute for in-depth methodological training. By highlighting best practices with their rationale, we hope this guidance will inspire further evolution of methods and tools that can advance the field.

The Role of Artificial Intelligence in Deciphering Diet-Disease Relationships: Case Studies

Modernization of society from a rural, hunter-gatherer setting into an urban and industrial habitat, with the associated dietary changes, has led to an increased prevalence of cardiometabolic and additional noncommunicable diseases, such as cancer, inflammatory bowel disease, and neurodegenerative and autoimmune disorders. However, while dietary sciences have been rapidly evolving to meet these challenges, validation and translation of experimental results into clinical practice remain limited for multiple reasons, including inherent ethnic, gender, and cultural interindividual variability, among other methodological, dietary reporting-related, and analytical issues. Recently, large clinical cohorts with artificial intelligence analytics have introduced new precision and personalized nutrition concepts that enable one to successfully bridge these gaps in a real-life setting. In this review, we highlight selected examples of case studies at the intersection between diet-disease research and artificial intelligence. We discuss their potential and challenges and offer an outlook toward the transformation of dietary sciences into individualized clinical translation.

Effect of the glucagon-like peptide-1 receptor agonist liraglutide, compared to caloric restriction, on appetite, dietary intake, body fat distribution and cardiometabolic biomarkers: A randomized trial in adults with obesity and prediabetes

AIMS

To investigate the hypothesis that weight loss with the glucagon-like peptide-1 receptor agonist (GLP-1RA) liraglutide alone would lead to a greater reduction in the proportion of fat to lean tissue mass when compared to caloric restriction (CR) alone, as well as when compared to treatment with sitagliptin, a dipeptidyl peptidase-4 (DPP-4) inhibitor, that also enhances GLP-1 activity - to determine the independent effects of each treatment.

METHODS

A total of 88 adults with obesity and prediabetes were randomized to 14 weeks of intervention with CR (-390 kcal/d), liraglutide (1.8 mg/d), or the dipeptidyl peptidase-4 inhibitor sitagliptin (100 mg/d) as a weight-neutral comparator. Changes between groups in appetite and hunger ratings measured via visual analogue scales, dietary intakes, body weight, body composition via dual energy x-ray absorptiometry, and resting energy expenditure via indirect calorimetry were assessed using the Kruskal-Wallis test or Pearson's chi-squared test.

RESULTS

Weight loss ≥5% of baseline body weight occurred in 44% of participants in the CR group, 22% of the liraglutide group and 5% of the sitagliptin group (p = 0.02). The ratio of fat to lean mass decreased by 6.5% in the CR group, 2.2% in the liraglutide group, and 0% in the sitagliptin group (p = 0.02). Visceral fat reduced by 9.5% in the CR group, 4.8% in the liraglutide group, and 0% in the sitagliptin group (p = 0.04). A spontaneous reduction in dietary simple carbohydrates in the CR group was associated with improved homeostatic model assessment of insulin resistance score (HOMA-IR).

CONCLUSIONS

Although both liraglutide and CR are valuable strategies for cardiometabolic risk reduction, CR was associated with greater weight loss and more favourable improvements in body composition than treatment with liraglutide alone. Differences in the response to each of these interventions enables patients to be stratified to the most optimal intervention for their personal risk factors.

Effect of Dietary Approaches on Glycemic Control in Patients with Type 2 Diabetes: A Systematic Review with Network Meta-Analysis of Randomized Trials

BACKGROUND

Dietary patterns play a critical role in diabetes management, while the best dietary pattern for Type 2 diabetes (T2DM) patients is still unclear. The aim of this network meta-analysis was to compare the impacts of various dietary approaches on the glycemic control of T2DM patients.

METHODS

Relevant studies were retrieved from PubMed, Embase, Web of Knowledge, Cochrane Central Register of Controlled Trials (CENTRAL), and other additional records (1949 to 31 July 2022). Eligible RCTs were those comparing different dietary approaches against each other or a control diet in individuals with T2DM for at least 6 months. We assessed the risk of bias of included studies with the Cochrane risk of bias tool and confidence of estimates with the Grading of Recommendations Assessment, Development, and Evaluation approach for network meta-analyses. In order to determine the pooled effect of each dietary approach relative to each other, we performed a network meta-analysis (NMA) for interventions for both HbA1c and fasting glucose, which enabled us to estimate the relative intervention effects by combing both direct and indirect trial evidence.

RESULTS

Forty-two RCTs comprising 4809 patients with T2DM were included in the NMA, comparing 10 dietary approaches (low-carbohydrate, moderate-carbohydrate, ketogenic, low-fat, high-protein, Mediterranean, Vegetarian/Vegan, low glycemic index, recommended, and control diets). In total, 83.3% of the studies were at a lower risk of bias or had some concerns. Findings of the NMA revealed that the ketogenic, low-carbohydrate, and low-fat diets were significantly effective in reducing HbA1c (viz., -0.73 (-1.19, -0.28), -0.69 (-1.32, -0.06), and -1.82 (-2.93, -0.71)), while moderate-carbohydrate, low glycemic index, Mediterranean, high-protein, and low-fat diets were significantly effective in reducing fasting glucose (viz., -1.30 (-1.92, -0.67), -1.26 (-2.26, -0.27), -0.95 (-1.51, -0.38), -0.89 (-1.60, -0.18) and -0.75 (-1.24, -0.27)) compared to a control diet. The clustered ranking plot for combined outcomes indicated the ketogenic, Mediterranean, moderate-carbohydrate, and low glycemic index diets had promising effects for controlling HbA1c and fasting glucose. The univariate meta-regressions showed that the mean reductions of HbA1c and fasting glucose were only significantly related to the mean weight change of the subjects.

CONCLUSIONS

For glycemic control in T2DM patients, the ketogenic diet, Mediterranean diet, moderate-carbohydrate diet, and low glycemic index diet were effective options. Although this study found the ketogenic diet superior, further high-quality and long-term studies are needed to strengthen its credibility.

A methodological review finds mismatch between overall and pairwise overlap analysis in a sample of overviews

OBJECTIVES

Overlap of primary studies is a key methodological challenge for overviews. There are limited reports of methods used to address overlap, and there is no detailed assessment of the corrected covered area (CCA) of a representative sample of overviews. To describe the approaches used to address overlap, and to estimate the overall and pairwise CCA.

METHODS

We searched PubMed for overviews published in 2018. Two authors conducted the screening process. We described the strategy used for assessing overlap, and calculated overall and pairwise CCA for each overview.

RESULTS

We analyzed a random sample of 30 out of 89 eligible articles. Eleven did not address the overlap. Of the remainder, most frequent strategies were visual assessment and discussion of overlap as a limitation. Median overall CCA among the included overviews was 6.7%. The pairwise analysis showed that 52.8% of SR pairs had slight overlap, while 28.3% had very high overlap.

CONCLUSION

Reported strategies for addressing overlap vary considerably among overview authors. The pairwise approach for assessing the CCA revealed highly overlapped pairs of SRs in overviews with overall slight overlap and vice versa. We encourage authors to complement the overall CCA assessment with a pairwise approach.

Position statement on nutrition therapy for overweight and obesity: nutrition department of the Brazilian association for the study of obesity and metabolic syndrome (ABESO-2022)

Obesity is a chronic disease resulting from multifactorial causes mainly related to lifestyle (sedentary lifestyle, inadequate eating habits) and to other conditions such as genetic, hereditary, psychological, cultural, and ethnic factors. The weight loss process is slow and complex, and involves lifestyle changes with an emphasis on nutritional therapy, physical activity practice, psychological interventions, and pharmacological or surgical treatment. Because the management of obesity is a long-term process, it is essential that the nutritional treatment contributes to the maintenance of the individual's global health. The main diet-related causes associated with excess weight are the high consumption of ultraprocessed foods, which are high in fats, sugars, and have high energy density; increased portion sizes; and low intake of fruits, vegetables, and grains. In addition, some situations negatively interfere with the weight loss process, such as fad diets that involve the belief in superfoods, the use of teas and phytotherapics, or even the avoidance of certain food groups, as has currently been the case for foods that are sources of carbohydrates. Individuals with obesity are often exposed to fad diets and, on a recurring basis, adhere to proposals with promises of quick solutions, which are not supported by the scientific literature. The adoption of a dietary pattern combining foods such as grains, lean meats, low-fat dairy, fruits, and vegetables, associated with an energy deficit, is the nutritional treatment recommended by the main international guidelines. Moreover, an emphasis on behavioral aspects including motivational interviewing and the encouragement for the individual to develop skills will contribute to achieve and maintain a healthy weight. Therefore, this Position Statement was prepared based on the analysis of the main randomized controlled studies and meta-analyses that tested different nutrition interventions for weight loss. Topics in the frontier of knowledge such as gut microbiota, inflammation, and nutritional genomics, as well as the processes involved in weight regain, were included in this document. This Position Statement was prepared by the Nutrition Department of the Brazilian Association for the Study of Obesity and Metabolic Syndrome (ABESO), with the collaboration of dietitians from research and clinical fields with an emphasis on strategies for weight loss.

Guidance to best tools and practices for systematic reviews

Data continue to accumulate indicating that many systematic reviews are methodologically flawed, biased, redundant, or uninformative. Some improvements have occurred in recent years based on empirical methods research and standardization of appraisal tools; however, many authors do not routinely or consistently apply these updated methods. In addition, guideline developers, peer reviewers, and journal editors often disregard current methodological standards. Although extensively acknowledged and explored in the methodological literature, most clinicians seem unaware of these issues and may automatically accept evidence syntheses (and clinical practice guidelines based on their conclusions) as trustworthy.A plethora of methods and tools are recommended for the development and evaluation of evidence syntheses. It is important to understand what these are intended to do (and cannot do) and how they can be utilized. Our objective is to distill this sprawling information into a format that is understandable and readily accessible to authors, peer reviewers, and editors. In doing so, we aim to promote appreciation and understanding of the demanding science of evidence synthesis among stakeholders. We focus on well-documented deficiencies in key components of evidence syntheses to elucidate the rationale for current standards. The constructs underlying the tools developed to assess reporting, risk of bias, and methodological quality of evidence syntheses are distinguished from those involved in determining overall certainty of a body of evidence. Another important distinction is made between those tools used by authors to develop their syntheses as opposed to those used to ultimately judge their work.Exemplar methods and research practices are described, complemented by novel pragmatic strategies to improve evidence syntheses. The latter include preferred terminology and a scheme to characterize types of research evidence. We organize best practice resources in a Concise Guide that can be widely adopted and adapted for routine implementation by authors and journals. Appropriate, informed use of these is encouraged, but we caution against their superficial application and emphasize their endorsement does not substitute for in-depth methodological training. By highlighting best practices with their rationale, we hope this guidance will inspire further evolution of methods and tools that can advance the field.

Guidance to best tools and practices for systematic reviews

Data continue to accumulate indicating that many systematic reviews are methodologically flawed, biased, redundant, or uninformative. Some improvements have occurred in recent years based on empirical methods research and standardization of appraisal tools; however, many authors do not routinely or consistently apply these updated methods. In addition, guideline developers, peer reviewers, and journal editors often disregard current methodological standards. Although extensively acknowledged and explored in the methodological literature, most clinicians seem unaware of these issues and may automatically accept evidence syntheses (and clinical practice guidelines based on their conclusions) as trustworthy.A plethora of methods and tools are recommended for the development and evaluation of evidence syntheses. It is important to understand what these are intended to do (and cannot do) and how they can be utilized. Our objective is to distill this sprawling information into a format that is understandable and readily accessible to authors, peer reviewers, and editors. In doing so, we aim to promote appreciation and understanding of the demanding science of evidence synthesis among stakeholders. We focus on well-documented deficiencies in key components of evidence syntheses to elucidate the rationale for current standards. The constructs underlying the tools developed to assess reporting, risk of bias, and methodological quality of evidence syntheses are distinguished from those involved in determining overall certainty of a body of evidence. Another important distinction is made between those tools used by authors to develop their syntheses as opposed to those used to ultimately judge their work.Exemplar methods and research practices are described, complemented by novel pragmatic strategies to improve evidence syntheses. The latter include preferred terminology and a scheme to characterize types of research evidence. We organize best practice resources in a Concise Guide that can be widely adopted and adapted for routine implementation by authors and journals. Appropriate, informed use of these is encouraged, but we caution against their superficial application and emphasize their endorsement does not substitute for in-depth methodological training. By highlighting best practices with their rationale, we hope this guidance will inspire further evolution of methods and tools that can advance the field.

A grape seed and bilberry extract reduces blood pressure in individuals at risk of developing type 2 diabetes: the PRECISE study, a double-blind placebo-controlled cross-over intervention study

Background

Type 2 Diabetes Mellitus (T2DM) is a major risk factor for the development of cardiometabolic diseases. T2DM prevention is largely based on weight-loss and whole diet changes, but intervention with dietary plant bioactives may also improve metabolic health.

Objective

To assess whether supplementation with bilberry and grape seed extract for 12 weeks improves cardiometabolic outcomes in individuals at risk of developing T2DM, and to determine whether individual treatment response is associated with differences in gut microbiota composition and levels of phenolic metabolites in blood and feces.

Methods

In the randomized, double-blind, placebo-controlled, cross-over PRECISE intervention study, 14 participants, aged ≥45 years, with a BMI >28 kg/m², and having an increased risk of T2DM, received a supplement containing 250 mg of bilberry plus 300 mg of grape seed extract, or 550 mg of a control extract, per day, for 12 weeks each. Blood samples were obtained for the assessment of HbA1c, fasting glucose, oral glucose tolerance tests, insulin, glucagon levels, total, LDL and HDL cholesterol, and phenolic acids. We also assessed advanced glycation end products in the skin, ambulatory 24 hours blood pressure, 7-day dietary intake by weighed food diaries, fecal levels of phenolic metabolites using LC-MS/MS and gut microbiota composition using 16S rRNA gene sequencing analysis.

Results

The combined bilberry and grape seed extract did not affect glucose and cholesterol outcomes, but it decreased systolic and diastolic ambulatory blood pressure by 4.7 (p < 0.001) and 2.3 (p = 0.0009) mmHg, respectively. Eight out of fourteen participants were identified as blood pressure 'responders'. These responders had higher levels of phenylpropionic and phenyllactic acids in their fecal samples, and a higher proportional abundance of Fusicatenibacter-related bacteria (p < 0.01) in their baseline stool samples.

Conclusion

Long-term supplementation with bilberry and grape seed extract can improve systolic and diastolic blood pressure in individuals at risk of T2DM. Individual responsiveness was correlated with the presence of certain fecal bacterial strains, and an ability to metabolize (epi)catechin into smaller phenolic metabolites.Clinical trial registry number: Research Registry (number 4084).

Guidance to Best Tools and Practices for Systematic Reviews

» Data continue to accumulate indicating that many systematic reviews are methodologically flawed, biased, redundant, or uninformative. Some improvements have occurred in recent years based on empirical methods research and standardization of appraisal tools; however, many authors do not routinely or consistently apply these updated methods. In addition, guideline developers, peer reviewers, and journal editors often disregard current methodological standards. Although extensively acknowledged and explored in the methodological literature, most clinicians seem unaware of these issues and may automatically accept evidence syntheses (and clinical practice guidelines based on their conclusions) as trustworthy.» A plethora of methods and tools are recommended for the development and evaluation of evidence syntheses. It is important to understand what these are intended to do (and cannot do) and how they can be utilized. Our objective is to distill this sprawling information into a format that is understandable and readily accessible to authors, peer reviewers, and editors. In doing so, we aim to promote appreciation and understanding of the demanding science of evidence synthesis among stakeholders. We focus on well-documented deficiencies in key components of evidence syntheses to elucidate the rationale for current standards. The constructs underlying the tools developed to assess reporting, risk of bias, and methodological quality of evidence syntheses are distinguished from those involved in determining overall certainty of a body of evidence. Another important distinction is made between those tools used by authors to develop their syntheses as opposed to those used to ultimately judge their work.» Exemplar methods and research practices are described, complemented by novel pragmatic strategies to improve evidence syntheses. The latter include preferred terminology and a scheme to characterize types of research evidence. We organize best practice resources in a Concise Guide that can be widely adopted and adapted for routine implementation by authors and journals. Appropriate, informed use of these is encouraged, but we caution against their superficial application and emphasize their endorsement does not substitute for in-depth methodological training. By highlighting best practices with their rationale, we hope this guidance will inspire further evolution of methods and tools that can advance the field.

Why Do People Gain Belly Fat in Rural Areas? A Study of Urinary Metal(loid)s and Abdominal Obesity in China

Obesity is prevalent in rural areas of China, and there are inconsistent findings regarding the association between metal(loid) exposure and the risk of obesity. Abdominal obesity (AOB), which reflects visceral fat abnormity, is a crucial factor in studying obesity-related diseases. We conducted a study measuring 20 urinary metal(loid)s, 13 health indicators, and the waist circumference (WC) in 1849 participants from 10 rural areas of China to investigate their relationships. In the single exposure models, we found that urinary chromium (Cr) was significantly associated with the odds of having AOB [adjusted odds ratio (OR) = 1.81 (95% confidence interval (CI): 1.24, 2.60)]. In the mixture exposure models, urinary Cr consistently emerged as the top contributor to AOB, while the overall effect of mixed metal(loid)s was positive toward the odds of having AOB [adjusted OR: 1.33 (95% CI: 1.00, 1.77)], as revealed from the quantile g-computation model. After adjusting for the effects of other metal(loid)s, we found that the elevation of apolipoprotein B and systolic blood pressure significantly mediated the association between urinary Cr and the odds of having AOB by 9.7 and 19.4%, respectively. Our results suggest that exposure to metal(loid)s is a key factor contributing to the prevalence of AOB and WC gain in rural areas of China.

Is Type 2 Diabetes Mellitus a Behavioural Disorder? An Evidence Review for Type 2 Diabetes Mellitus Prevention and Remission through Lifestyle Modification

The prevalence of type 2 diabetes mellitus (T2DM) is steadily rising worldwide due to an increasingly sedentary lifestyle combined with unhealthy food habits. Currently, the burden of diabetes on healthcare systems is unprecedented and rising daily. Several observational studies and randomized controlled trials provide clinical evidence that T2DM remission is possible by adopting dietary interventions and a strict exercise training protocol. Notably, these studies provide ample evidence for remission in patients with T2DM or for prevention in those with risk factors for the disease through various non-pharmacological behavioural interventions. In this article, we present two clinical cases of individuals who showed remission from T2DM/prediabetes via behavioural changes, especially through the adoption of a low-energy diet and exercise. We also discuss the recent advances in T2DM and obesity research, focusing on nutritional interventions and exercise and their benefits for weight loss, improved metabolic profile, enhanced glycaemic control and remission of diabetes.

Quality of low-carbohydrate diets among Australian post-partum women: Cross-sectional analysis of a national population-based cohort study

Low-carbohydrate diets (LCDs) are popular among people attempting weight loss and recommended for pregnant women with gestational diabetes (GDM), but they may increase health risks if nutritionally inadequate. We aimed to describe the dietary intake of post-partum women according to their relative carbohydrate intake, overall, and among women attempting weight loss or diagnosed with GDM in their recent pregnancy. This cross-sectional population-based cohort study included 2093 post-partum women aged 25-36 years who participated in the Australian Longitudinal Study on Women's Health. Dietary intake was assessed using a validated food frequency questionnaire. Relative carbohydrate intake was determined using a previously developed LCD score. Data were weighted to account for oversampling of women from rural/remote areas. More than half of women (n[weighted] = 1362, 66.3%) were trying to lose weight, and 4.6% (n[weighted]=88) had GDM in their recent pregnancy. Women with the lowest relative carbohydrate intake (LCD score quartile 4) consumed 36.8% of total energy intake from carbohydrates, and had a lower intake of refined grains, whole grains, fruit and fruit juice, and a higher intake of red and processed meat, compared with women with the highest relative carbohydrate intake (quartile 1). Different food groups, both healthy and unhealthy, were restricted depending on whether women were attempting weight loss and had recent GDM. These findings may reflect a lack of knowledge among post-partum women on carbohydrates and dietary guidelines. Health professionals may have an important role in providing advice and support for post-partum women who wish to restrict their carbohydrate intake, to ensure optimal diet quality.

Low carbohydrate high fat-diet in real life assessed by diet history interviews

BACKGROUND

Low carbohydrate high fat (LCHF) diet has been a popular low carbohydrate diet in Sweden for 15 years. Many people choose LCHF to lose weight or control diabetes, but there are concerns about the effect on long-term cardiovascular risks. There is little data on how a LCHF diet is composed in real-life. The aim of this study was to evaluate the dietary intake in a population with self-reported adherence to a LCHF diet.

METHODS

A cross-sectional study of 100 volunteers that considered themselves eating LCHF was conducted. Diet history interviews (DHIs) and physical activity monitoring for validation of the DHIs were performed.

RESULTS

The validation shows acceptable agreement of measured energy expenditure and reported energy intake. Median carbohydrate intake was 8.7 E% and 63% reported carbohydrate intake at potentially ketogenic levels. Median protein intake was 16.9 E%. The main source of energy was dietary fats (72.0 E%). Intake of saturated fat was 32 E% and cholesterol was 700 mg per day, both of which exceeded the recommended upper limits according to nutritional guidelines. Intake of dietary fiber was very low in our population. The use of dietary supplements was high, and it was more common to exceed the recommended upper limits of micronutrients than to have an intake below the lower limits.

CONCLUSIONS

Our study indicates that in a well-motivated population, a diet with very low carbohydrate intake can be sustained over time and without apparent risk of deficiencies. High intake of saturated fats and cholesterol as well as low intake of dietary fiber remains a concern.

Carbohydrate Intakes below Recommendations with a High Intake of Fat Are associated with Higher Prevalence of Metabolic Syndrome

BACKGROUND

More than one-third of adults in the United States have metabolic syndrome, and dietary carbohydrate intake may modify the likelihood of developing this condition. Currently, there is a lack of consistent evidence demonstrating the relationship between carbohydrate intake that falls below recommendations and metabolic syndrome. Not accounting for the differences in fatty acid classes of these dietary patterns may be a reason for inconsistent findings.

OBJECTIVE

This study evaluated the association between a carbohydrate intake below recommendations and metabolic syndrome stratified by fat quantity and fatty acid classes in a nationally representative sample of US adults.

DESIGN

This cross-sectional study acquired data on food and nutrient intake and markers of metabolic syndrome from respondents in the National Health and Nutrition Examination Survey 1999-2018.

PARTICIPANTS/SETTING

This study included 19,078 respondents who were aged 20 years or older, had reliable and complete data on food and nutrient intake and markers of metabolic syndrome, and were not pregnant or breastfeeding.

MAIN OUTCOME MEASURES

The main outcome was prevalence of metabolic syndrome.

STATISTICAL ANALYSES PERFORMED

Usual dietary intake was estimated using the National Cancer Institute's usual intake methodology. Multivariable logistic regression models assessed the relative odds of prevalent metabolic syndrome between those who had a carbohydrate intake below recommendations and those who met carbohydrate recommendations.

RESULTS

Those who had a carbohydrate intake below recommendations had 1.067 (95% CI 1.063 to 1.071) times greater odds of having metabolic syndrome compared with those who met carbohydrate recommendations (P < 0.001). High intake of fat of any class was associated with higher odds of metabolic syndrome (total fat: 1.271, 95% CI 1.256 to 1.286; saturated fatty acid: 1.072, 95% CI 1.060 to 1.085; monounsaturated fatty acid: 1.317, 95% CI 1.300 to 1.333; polyunsaturated fatty acid: 1.056, 95% CI 1.047 to 1.066; P < 0.001 for all comparisons) in those who had a carbohydrate intake below recommendations.

CONCLUSIONS

The odds of prevalent metabolic syndrome were higher among individuals who had a carbohydrate intake below recommendations compared with individuals who met carbohydrate recommendations.

Macronutrient composition and its effect on body composition changes during weight loss therapy in patients with non-alcoholic fatty liver disease: Secondary analysis of a randomized controlled trial

OBJECTIVES

Dietary composition may affect body composition during weight loss therapy. We tested the hypothesis of whether dietary macronutrient composition influences the reduction of total abdominal adipose tissue, subcutaneous adipose tissue (SAT), or visceral adipose tissue (VAT) during weight loss.

METHODS

Dietary macronutrient composition and body composition were analyzed as a secondary outcome of a randomized controlled trial of 62 participants with non-alcoholic fatty liver disease. Patients were randomly assigned to a calorie-restricted intermittent fasting (5:2), calorie-restricted low-carbohydrate high-fat (LCHF), or healthy lifestyle advice (standard-of-care) diet in a 12-wk intervention phase. Dietary intake was assessed by self-reported 3-d food diaries and by characterization of total plasma fatty acid profile. Percentage of energy intake (E%) from different macronutrients was calculated. Body composition was assessed by magnetic resonance imaging and anthropometric measurements.

RESULTS

The macronutrient composition differed significantly between the 5:2 (fat 36 E% and carbohydrates 43 E%) and the LCHF (fat 69 E% and carbohydrates 9 E%) groups (P < 0.001). Weight loss was similar in the 5:2 and LCHF groups (-7.2 [SD = 3.4] kg versus 8.0 [SD = 4.8] kg; P = 0.44) and significantly larger than for standard of care (-2.5 kg [SD = 2.3]; P < 0.001). The volume of total abdominal fat, adjusted for height, decreased on average by 4.7% (standard of care), 14.3% (5:2), and 17.7% (LCHF), with no significant differences between the 5:2 and LHCF groups (P = 0.32). VAT and SAT, adjusted for height, decreased on average by 17.1% and 12.7% for 5:2, respectively, and by 21.2% and 17.9% for LCHF, with no significant group differences (VAT [P = 0.16] and SAT [P = 0.10]). VAT was mobilized to a greater extent than SAT in all diets.

CONCLUSIONS

The 5:2 and LCHF diets had similar effects on changes in intraabdominal fat mass and anthropometrics during weight loss. This might indicate that overall weight loss is more important than diet composition to achieve changes in total abdominal adipose tissue, VAT, or SAT. The results of the present study suggest that there is a need for further studies on the effect of diet composition on body composition changes during weight loss therapy.

Guidance to best tools and practices for systematic reviews1

Data continue to accumulate indicating that many systematic reviews are methodologically flawed, biased, redundant, or uninformative. Some improvements have occurred in recent years based on empirical methods research and standardization of appraisal tools; however, many authors do not routinely or consistently apply these updated methods. In addition, guideline developers, peer reviewers, and journal editors often disregard current methodological standards. Although extensively acknowledged and explored in the methodological literature, most clinicians seem unaware of these issues and may automatically accept evidence syntheses (and clinical practice guidelines based on their conclusions) as trustworthy.A plethora of methods and tools are recommended for the development and evaluation of evidence syntheses. It is important to understand what these are intended to do (and cannot do) and how they can be utilized. Our objective is to distill this sprawling information into a format that is understandable and readily accessible to authors, peer reviewers, and editors. In doing so, we aim to promote appreciation and understanding of the demanding science of evidence synthesis among stakeholders. We focus on well-documented deficiencies in key components of evidence syntheses to elucidate the rationale for current standards. The constructs underlying the tools developed to assess reporting, risk of bias, and methodological quality of evidence syntheses are distinguished from those involved in determining overall certainty of a body of evidence. Another important distinction is made between those tools used by authors to develop their syntheses as opposed to those used to ultimately judge their work.Exemplar methods and research practices are described, complemented by novel pragmatic strategies to improve evidence syntheses. The latter include preferred terminology and a scheme to characterize types of research evidence. We organize best practice resources in a Concise Guide that can be widely adopted and adapted for routine implementation by authors and journals. Appropriate, informed use of these is encouraged, but we caution against their superficial application and emphasize their endorsement does not substitute for in-depth methodological training. By highlighting best practices with their rationale, we hope this guidance will inspire further evolution of methods and tools that can advance the field.

Current Evidence Concerning Effects of Ketogenic Diet and Intermittent Fasting in Patients with Nonalcoholic Fatty Liver

Nonalcoholic fatty liver disease (NAFLD) is emerging globally, while no therapeutic medication has been approved as an effective treatment to date, lifestyle intervention through dietary modification and physical exercise plays a critical role in NAFLD management. In terms of dietary modification, Mediterranean diet is the most studied dietary pattern and is recommended in many guidelines, however, it may not be feasible and affordable for many patients. Recently, a ketogenic diet and intermittent fasting have gained public attention and have been studied in the role of weight management. This article reviews specifically whether these trendy dietary patterns have an effect on NAFLD outcomes regarding intrahepatic fat content, fibrosis, and liver enzymes, the scientific rationales behind these particular dietary patterns, as well as the safety concerns in some certain patient groups.

Effects of low-carbohydrate diets versus low-fat diets on metabolic risk factors in overweight and obese adults: A meta-analysis of randomized controlled trials

Background and aims

Low-carbohydrate diets (LCD) and low-fat diets (LFD) have shown beneficial effects on the management of obesity. Epidemiological studies were conducted to compare the effects of the two diets. However, the results were not always consistent. This study aimed to conduct a meta-analysis to compare the long-term effects of LCD and LFD on metabolic risk factors and weight loss in overweight and obese adults.

Methods

We performed a systematic literature search up to 30 March, 2022 in PubMed, EMBASE, and Cochrane Library. The meta-analysis compared the effects of LCD (carbohydrate intake ≤ 40%) with LFD (fat intake < 30%) on metabolic risk factors and weight loss for ≥6 months. Subgroup analyses were performed based on participant characteristics, dietary energy intake, and the proportions of carbohydrates.

Results

33 studies involving a total of 3,939 participants were included. Compared with participants on LFD, participants on LCD had a greater reduction in triglycerides (–0.14 mmol/L; 95% CI, –0.18 to –0.10 mmol/L), diastolic blood pressure (–0.87 mmHg; 95% CI, –1.41 to –0.32 mmHg), weight loss (–1.33 kg; 95% CI, –1.79 to –0.87 kg), and a greater increase in high-density lipoprotein cholesterol (0.07 mmol/L; 95% CI, 0.06 to 0.09 mmol/L) in 6–23 months. However, the decrease of total cholesterol (0.14 mmol/L; 95% CI, 0.07 to 0.20 mmol/L) and low-density lipoprotein cholesterol (0.10 mmol/L; 95% CI, 0.06 to 0.14 mmol/L) was more conducive to LFD in 6–23 months. There was no difference in benefits between the two diets after 24 months. Subgroup analyses showed no significant difference in the reduction of total cholesterol, low-density lipoprotein cholesterol, and blood pressure between the two diets in participants with diabetes, hypertension, or hyperlipidemia.

Conclusion

The results suggest that LCD and LFD may have specific effects on metabolic risk factors and weight loss in overweight and obese adults over 6 months. At 24 months, the effects on weight loss and improvement of metabolic risk factors were at least the same. These indicated that we might choose different diets to manage the overweight and obese subjects. However, the long-term clinical efficacy and effects of various sources of carbohydrates or fat in the two diets need to be studied in the future.

The role of prenatal vitamin D on the development of childhood asthma and wheeze: An umbrella review of systematic reviews and meta-analyses

BACKGROUND & OBJECTIVE

It has been suggested that prenatal vitamin D plays a role in the development of childhood asthma and wheeze. Several systematic reviews have been conducted, but the results are inconsistent, and the methodological quality has not been studied. Therefore, the objective of this umbrella review was to assess the internal validity of the evidence base and the evidence for an association between prenatal vitamin D and asthma or wheezing in the offspring.

METHODS

We searched the electronic databases Embase, PubMed, and Cochrane Library for studies on prenatal vitamin D using search words such as vitamin D, 25-hydroxyvitamin D, calcidiol, fetal, and neonatal. The search was conducted in June 2020, and the databases were searched from their date of establishment. We included systematic reviews and/or meta-analyses of experimental and observational studies assessing the association between prenatal vitamin D or asthma and wheeze. We excluded narrative reviews, commentaries, and other umbrella reviews. The methodological quality of systematic reviews was assessed using AMSTAR 2 tool. PROSPERO reg. no. CRD42020151329.

RESULTS

We identified 22 eligible systematic reviews (17 on asthma and 20 on wheeze). Using the AMSTAR 2 quality assessment tool, the methodological quality was rated as critically low in 21 out of 22 systematic reviews, suggesting that previous reviews and meta-analyses did not provide accurate and comprehensive summaries of the included studies and that conclusions reached were potentially flawed. The majority of the included reviews reported that prenatal vitamin D reduces the risk of wheeze in the offspring.

CONCLUSION

Prior to informing public guidelines, high-quality systematic reviews of the current evidence are greatly warranted.

The association between low carbohydrate diet scores and cardiometabolic risk factors in Chinese adults

Epidemiological studies on the association between the low carbohydrate diet (LCD) score and cardiovascular disease risk factors have limited and inconsistent results. Data are from the baseline survey of Community-based Cohort Study on Nervous System Diseases. A total of 4609 adults aged ≥18 years were included in the study. Dietary data were assessed using a validated semi-quantitative Food Frequency Questionnaire. Multivariable logistic regression analyses were used to estimate relationships of three LCD scores with low high-density lipoprotein cholesterol (HDL-C), high low-density lipoprotein cholesterol (LDL-C), hypercholesterolemia, hypertriglyceridemia, impaired fasting glucose (IFG), high blood pressure, and hyperuricemia after adjusting for potential confounders. A higher LCD score was negatively associated with low HDL-C [OR (95%CI): 0.65 (0.50, 0.83), P=0.0001] and IFG [OR (95%CI): 0.65 (0.51, 0.81), P=0.001] after the final adjustment. However, there are gender differences in this result. Males in the highest quintile of the animal-based or plant-based LCD scores showed a decreased risk of low HDL-C, and females in the highest quintile of the animal-based or plant-based LCD scores showed a decreased risk of IFG than those in the lowest quintile of the LCD scores. These results suggest that gender differences should be considered when using LCD to treat dyslipidemia and reduce fasting blood glucose.

Assessing the Nutrient Status of Low Carbohydrate, High-Fat (LCHF) Meal Plans in Children: A Hypothetical Case Study Design

There is well-established evidence for low-carbohydrate, high-fat (LCHF) diets in the management of chronic health conditions in adults. The natural next step is to understand the potential risks and benefits of LCHF diets for children, where they may have useful applications for general health and a variety of chronic health conditions. It is vital that any diet delivers sufficient micronutrients and energy to ensure health, wellbeing, and growth. This descriptive study assesses the nutrient and energy status of LCHF sample meal plans for children. We designed four meal plans for hypothetical weight-stable male and female children (11 years) and adolescents (16 years). Carbohydrates were limited to ≤80 g, protein was set at 15–25% of the total energy, and fat supplied the remaining calories. Using FoodWorks dietary analysis software, data were assessed against the national Australian/New Zealand nutrient reference value (NRV) thresholds for children and adolescents. All meal plans exceeded the minimum NRV thresholds for all micronutrients; protein slightly exceeded the AMDR recommendations by up to three percentage points. This study demonstrates that LCHF meal plans can be energy-, protein-, and micronutrient-replete for children and adolescents. As with any dietary approach, well-formulated meals and careful planning are key to achieving the optimal nutrient status.

Influence of almond and coconut flours on Ketogenic, Gluten-Free cupcakes

Ketogenic, gluten-free cupcakes containing varying amounts of almond and coconut flours were evaluated for textural and sensory attributes. Coconut-flour particle-size influenced cupcake volume and crumb structure, with smaller flour-particle size resulting in increased volume and decreased crumb density. Although almond-flour particle size itself did not directly influence cupcake properties, volume increases were observed in cupcakes with higher percentages of almond flour. Addition of coconut flour increased cell size and decreased cell density. Mechanical testing showed almond flour resulted in a cupcake that was more tender. Adhesion and cohesion values showed no statistical difference after 24 h and minimal change at subsequent evaluation periods. Quantitative descriptive analysis and consumer acceptance evaluation indicated that cupcakes containing almond flour were more moist and tender, and were preferred over cupcakes made with only coconut flour. Almond and coconut flours may be used in gluten-free, ketogenic cupcakes, with almond flour performing better in evaluated parameters.

Use of an mHealth Ketogenic Diet App Intervention and User Behaviors Associated With Weight Loss in Adults With Overweight or Obesity: Secondary Analysis of a Randomized Clinical Trial

Background

Low-carbohydrate ketogenic diets are a viable method to lose weight that have regained popularity in recent years. Technology in the form of mobile health (mHealth) apps allows for scalable and remote delivery of such dietary interventions and are increasingly being used by the general population without direct medical supervision. However, it is currently unknown which factors related to app use and user behavior are associated with successful weight loss.

Objective

First, to describe and characterize user behavior, we aim to examine characteristics and user behaviors over time of participants who were enrolled in a remotely delivered clinical weight loss trial that tested an mHealth ketogenic diet app paired with a breath acetone biofeedback device. Second, to identify variables of importance to weight loss at 12 weeks that may offer insight for future development of dietary mHealth interventions, we aim to explore which app- and adherence-related user behaviors characterized successful weight loss.

Methods

We analyzed app use and self-reported questionnaire data from 75 adults with overweight or obesity who participated in the intervention arm of a previous weight loss study. We examined data patterns over time through linear mixed models and performed correlation, linear regression, and causal mediation analyses to characterize diet-, weight-, and app-related user behavior associated with weight loss.

Results

In the context of a low-carbohydrate ketogenic diet intervention delivered remotely through an mHealth app paired with a breath acetone biofeedback device, self-reported dietary adherence seemed to be the most important factor to predict weight loss (β=–.31; t₅₄=–2.366; P=.02). Furthermore, self-reported adherence mediated the relationship between greater app engagement (from c=–0.008, 95% CI –0.014 to –0.0019 to c’=–0.0035, 95% CI –0.0094 to 0.0024) or higher breath acetone levels (from c=–1.34, 95% CI –2.28 to –0.40 to c’=–0.40, 95% CI –1.42 to 0.62) and greater weight loss, explaining a total of 27.8% and 28.8% of the variance in weight loss, respectively. User behavior (compliance with weight measurements and app engagement) and adherence-related aspects (breath acetone values and self-reported dietary adherence) over time differed between individuals who achieved a clinically significant weight loss of >5% and those who did not.

Conclusions

Our in-depth examination of app- and adherence-related user behaviors offers insight into factors associated with successful weight loss in the context of mHealth interventions. In particular, our finding that self-reported dietary adherence was the most important metric predicting weight loss may aid in the development of future mHealth dietary interventions.

Trial Registration

ClinicalTrials.gov NCT04165707; https://clinicaltrials.gov/ct2/show/NCT04165707

International Registered Report Identifier (IRRID)

RR2-10.2196/19053

Low-carbohydrate versus balanced-carbohydrate diets for reducing weight and cardiovascular risk

BACKGROUND

Debates on effective and safe diets for managing obesity in adults are ongoing. Low-carbohydrate weight-reducing diets (also known as 'low-carb diets') continue to be widely promoted, marketed and commercialised as being more effective for weight loss, and healthier, than 'balanced'-carbohydrate weight-reducing diets.

OBJECTIVES

To compare the effects of low-carbohydrate weight-reducing diets to weight-reducing diets with balanced ranges of carbohydrates, in relation to changes in weight and cardiovascular risk, in overweight and obese adults without and with type 2 diabetes mellitus (T2DM).

SEARCH METHODS

We searched MEDLINE (PubMed), Embase (Ovid), the Cochrane Central Register of Controlled Trials (CENTRAL), Web of Science Core Collection (Clarivate Analytics), ClinicalTrials.gov and WHO International Clinical Trials Registry Platform (ICTRP) up to 25 June 2021, and screened reference lists of included trials and relevant systematic reviews. Language or publication restrictions were not applied.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) in adults (18 years+) who were overweight or living with obesity, without or with T2DM, and without or with cardiovascular conditions or risk factors. Trials had to compare low-carbohydrate weight-reducing diets to balanced-carbohydrate (45% to 65% of total energy (TE)) weight-reducing diets, have a weight-reducing phase of 2 weeks or longer and be explicitly implemented for the primary purpose of reducing weight, with or without advice to restrict energy intake.  DATA COLLECTION AND ANALYSIS: Two review authors independently screened titles and abstracts and full-text articles to determine eligibility; and independently extracted data, assessed risk of bias using RoB 2 and assessed the certainty of the evidence using GRADE. We stratified analyses by participants without and with T2DM, and by diets with weight-reducing phases only and those with weight-reducing phases followed by weight-maintenance phases. Primary outcomes were change in body weight (kg) and the number of participants per group with weight loss of at least 5%, assessed at short- (three months to < 12 months) and long-term (≥ 12 months) follow-up.

MAIN RESULTS

We included 61 parallel-arm RCTs that randomised 6925 participants to either low-carbohydrate or balanced-carbohydrate weight-reducing diets. All trials were conducted in high-income countries except for one in China. Most participants (n = 5118 randomised) did not have T2DM. Mean baseline weight across trials was 95 kg (range 66 to 132 kg). Participants with T2DM were older (mean 57 years, range 50 to 65) than those without T2DM (mean 45 years, range 22 to 62). Most trials included men and women (42/61; 3/19 men only; 16/19 women only), and people without baseline cardiovascular conditions, risk factors or events (36/61). Mean baseline diastolic blood pressure (DBP) and low-density lipoprotein (LDL) cholesterol across trials were within normal ranges. The longest weight-reducing phase of diets was two years in participants without and with T2DM. Evidence from studies with weight-reducing phases followed by weight-maintenance phases was limited. Most trials investigated low-carbohydrate diets (> 50 g to 150 g per day or < 45% of TE; n = 42), followed by very low (≤ 50 g per day or < 10% of TE; n = 14), and then incremental increases from very low to low (n = 5). The most common diets compared were low-carbohydrate, balanced-fat (20 to 35% of TE) and high-protein (> 20% of TE) treatment diets versus control diets balanced for the three macronutrients (24/61). In most trials (45/61) the energy prescription or approach used to restrict energy intake was similar in both groups. We assessed the overall risk of bias of outcomes across trials as predominantly high, mostly from bias due to missing outcome data. Using GRADE, we assessed the certainty of evidence as moderate to very low across outcomes.  Participants without and with T2DM lost weight when following weight-reducing phases of both diets at the short (range: 12.2 to 0.33 kg) and long term (range: 13.1 to 1.7 kg).  In overweight and obese participants without T2DM: low-carbohydrate weight-reducing diets compared to balanced-carbohydrate weight-reducing diets (weight-reducing phases only) probably result in little to no difference in change in body weight over three to 8.5 months (mean difference (MD) -1.07 kg, (95% confidence interval (CI) -1.55 to -0.59, I2 = 51%, 3286 participants, 37 RCTs, moderate-certainty evidence) and over one to two years (MD -0.93 kg, 95% CI -1.81 to -0.04, I2 = 40%, 1805 participants, 14 RCTs, moderate-certainty evidence); as well as change in DBP and LDL cholesterol over one to two years. The evidence is very uncertain about whether there is a difference in the number of participants per group with weight loss of at least 5% at one year (risk ratio (RR) 1.11, 95% CI 0.94 to 1.31, I2 = 17%, 137 participants, 2 RCTs, very low-certainty evidence).  In overweight and obese participants with T2DM: low-carbohydrate weight-reducing diets compared to balanced-carbohydrate weight-reducing diets (weight-reducing phases only) probably result in little to no difference in change in body weight over three to six months (MD -1.26 kg, 95% CI -2.44 to -0.09, I2 = 47%, 1114 participants, 14 RCTs, moderate-certainty evidence) and over one to two years (MD -0.33 kg, 95% CI -2.13 to 1.46, I2 = 10%, 813 participants, 7 RCTs, moderate-certainty evidence); as well in change in DBP, HbA1c and LDL cholesterol over 1 to 2 years. The evidence is very uncertain about whether there is a difference in the number of participants per group with weight loss of at least 5% at one to two years (RR 0.90, 95% CI 0.68 to 1.20, I2 = 0%, 106 participants, 2 RCTs, very low-certainty evidence).  Evidence on participant-reported adverse effects was limited, and we could not draw any conclusions about these.  AUTHORS' CONCLUSIONS: There is probably little to no difference in weight reduction and changes in cardiovascular risk factors up to two years' follow-up, when overweight and obese participants without and with T2DM are randomised to either low-carbohydrate or balanced-carbohydrate weight-reducing diets.

Diets for weight management in adults with type 2 diabetes: an umbrella review of published meta-analyses and systematic review of trials of diets for diabetes remission

AIMS/HYPOTHESIS

Weight reduction is fundamental for type 2 diabetes management and remission, but uncertainty exists over which diet type is best to achieve and maintain weight loss. We evaluated dietary approaches for weight loss, and remission, in people with type 2 diabetes to inform practice and clinical guidelines.

METHODS

First, we conducted a systematic review of published meta-analyses of RCTs of weight-loss diets. We searched MEDLINE (Ovid), PubMed, Web of Science and Cochrane Database of Systematic Reviews, up to 7 May 2021. We synthesised weight loss findings stratified by diet types and assessed meta-analyses quality with A Measurement Tool to Assess Systematic Reviews (AMSTAR) 2. We assessed certainty of pooled results of each meta-analysis using Grading of Recommendations, Assessment, Development and Evaluations (GRADE) (PROSPERO CRD42020169258). Second, we conducted a systematic review of any intervention studies reporting type 2 diabetes remission with weight-loss diets, in MEDLINE (via PubMed), Embase and Cochrane Central Register of Controlled Trials, up to 10 May 2021. Findings were synthesised by diet type and study quality (Cochrane Risk of Bias tool 2.0 and Risk Of Bias In Non-randomised Studies - of Interventions [ROBINS-I]), with GRADE applied (PROSPERO CRD42020208878).

RESULTS

We identified 19 meta-analyses of weight-loss diets, involving 2-23 primary trials (n = 100-1587), published 2013-2021. Twelve were 'critically low' or 'low' AMSTAR 2 quality, with seven 'high' quality. Greatest weight loss was reported with very low energy diets, 1.7-2.1 MJ/day (400-500 kcal) for 8-12 weeks (high-quality meta-analysis, GRADE low), achieving 6.6 kg (95% CI -9.5, -3.7) greater weight loss than low-energy diets (4.2-6.3 MJ/day [1000-1500 kcal]). Formula meal replacements (high quality, GRADE moderate) achieved 2.4 kg (95% CI -3.3, -1.4) greater weight loss over 12-52 weeks. Low-carbohydrate diets were no better for weight loss than higher-carbohydrate/low-fat diets (high quality, GRADE high). High-protein, Mediterranean, high-monounsaturated-fatty-acid, vegetarian and low-glycaemic-index diets all achieved minimal (0.3-2 kg) or no difference from control diets (low to critically low quality, GRADE very low/moderate). For type 2 diabetes remission, of 373 records, 16 met inclusion criteria. Remissions at 1 year were reported for a median 54% of participants in RCTs including initial low-energy total diet replacement (low-risk-of-bias study, GRADE high), and 11% and 15% for meal replacements and Mediterranean diets, respectively (some concerns for risk of bias in studies, GRADE moderate/low). For ketogenic/very low-carbohydrate and very low-energy food-based diets, the evidence for remission (20% and 22%, respectively) has serious and critical risk of bias, and GRADE certainty is very low.

CONCLUSIONS/INTERPRETATION

Published meta-analyses of hypocaloric diets for weight management in people with type 2 diabetes do not support any particular macronutrient profile or style over others. Very low energy diets and formula meal replacement appear the most effective approaches, generally providing less energy than self-administered food-based diets. Programmes including a hypocaloric formula 'total diet replacement' induction phase were most effective for type 2 diabetes remission. Most of the evidence is restricted to 1 year or less. Well-conducted research is needed to assess longer-term impacts on weight, glycaemic control, clinical outcomes and diabetes complications.

Nutrition Concepts for the Treatment of Obesity in Adults

Obesity caused by a positive energy balance is a serious health burden. Studies have shown that obesity is the major risk factor for many diseases like type 2 diabetes mellitus, coronary heart diseases, or various types of cancer. Therefore, the prevention and treatment of increased body weight are key. Different evidence-based treatment approaches considering weight history, body mass index (BMI) category, and co-morbidities are available: lifestyle intervention, formula diet, drugs, and bariatric surgery. For all treatment approaches, behaviour change techniques, reduction in energy intake, and increasing energy expenditure are required. Self-monitoring of diet and physical activity provides an effective behaviour change technique for weight management. Digital tools increase engagement rates for self-monitoring and have the potential to improve weight management. The objective of this narrative review is to summarize current available treatment approaches for obesity, to provide a selective overview of nutrition trends, and to give a scientific viewpoint for various nutrition concepts for weight loss.

Nonsurgical weight loss interventions: A systematic review of systematic reviews and meta-analyses

Access to bariatric surgery to treat obesity is limited and has long wait times. Many adults are seeking nonsurgical weight loss support. Our study objective was to conduct a systematic review of nonsurgical weight loss interventions. PubMed, EMBASE, CINAHL, PsycInfo, and the CochraneLibrary were searched. Inclusion criteria were adults 18 + with a BMI > 25 enrolled in minimum a 3-month nonsurgical weight loss intervention. Studies were independently extracted and assessed for quality using A MeaSurement Tool to Assess systematic Reviews 2 (AMSTAR2). Pooled analyses were extracted, graded for evidence quality, and summarized. A total of 1065 studies were assessed for eligibility; 815 screened and 236 full-texts assessed. Sixty-four meta-analyses met eligibility criteria: 1180 RCTs with 184,605 study participants. Studies were categorized as diets (n = 13), combination therapies (n = 10), alternative (n = 16), technology (n = 10), behavioral (n = 5), physical activity (n = 6), and pharmacotherapy (n = 3). In 80% of studies, significant weight losses were reported ranging from 0.34-8.73 k in favor of the intervention. The most effective nonsurgical weight loss interventions were diets, either low-carbohydrate or low-fat diets, followed for 6 months; combination therapy including meal replacements plus enhanced support; and pharmacotherapy followed for 12 months. Although significant weight losses were reported for other types of interventions such as physical activity and technology, the majority of studies reported weight losses less than 2 kgs.

Association of the low-carbohydrate dietary pattern with postpartum weight retention in women

Low-carbohydrate diets (LCD) have been considered a popular dietary strategy for weight loss. However, the association of the low-carbohydrate dietary pattern with postpartum weight retention (PPWR) in women remains unknown. The present study involved 426 women from a prospective mother-infant cohort study. Overall, animal or plant LCD scores, which represent adherence to different low-carbohydrate dietary patterns, were calculated using diet intake information assessed by three consecutive 24 h dietary surveys. PPWR was assessed by the difference of weight at 1 year postpartum minus the pre-pregnancy weight. After adjusting for potential confounding variables, women in higher quartiles of total and animal-based LCD scores had a significantly lower body weight and weight retention at 1 year postpartum (P < 0.05). The multivariable-adjusted ORs of substantial PPWR (≥5 kg), comparing the highest with the lowest quartile, were 0.47 (95% confidence interval 0.23-0.96) for the total LCD score (P = 0.021 for trend) and 0.38 (95% confidence interval 0.19-0.77) for the animal-based LCD score (P = 0.019 for trend), while this association was significantly attenuated by rice, glycemic load, fish, poultry, animal fat and animal protein (P for trend <0.05). A high score for plant-based LCD was not significantly associated with the risk of PPWR (P > 0.05). The findings suggested that a low-carbohydrate dietary pattern, particularly with high protein and fat intake from animal-source foods, is associated with a decreased risk of weight retention at 1 year postpartum. This association was mainly due to low intake of glycemic load and high intake of fish and poultry.

Individual Postprandial Glycemic Responses to Diet in n-of-1 Trials: Westlake N-of-1 Trials for Macronutrient Intake (WE-MACNUTR)

BACKGROUND

The role of different types and quantities of macronutrients on human health has been controversial, and the individual response to dietary macronutrient intake needs more investigation.

OBJECTIVES

We aimed to use an 'n-of-1' study design to investigate the individual variability in postprandial glycemic response when eating diets with different macronutrient distributions among apparently healthy adults.

METHODS

Thirty apparently healthy young Chinese adults (women, 68%) aged between 22 and 34 y, with BMI between 17.2 and 31.9 kg/m2, were provided with high-fat, low-carbohydrate (HF-LC, 60-70% fat, 15-25% carbohydrate, 15% protein, of total energy) and low-fat, high-carbohydrate (LF-HC, 10-20% fat, 65-75% carbohydrate, 15% protein) diets, for 6 d wearing continuous glucose monitoring systems, respectively, in a randomized sequence, interspersed by a 6-d wash-out period. Three cycles were conducted. The primary outcomes were the differences of maximum postprandial glucose (MPG), mean amplitude of glycemic excursions (MAGE), and AUC24 between intervention periods of LF-HC and HF-LC diets. A Bayesian model was used to predict responders with the posterior probability of any 1 of the 3 outcomes reaching a clinically meaningful difference.

RESULTS

Twenty-eight participants were included in the analysis. Posterior probability of reaching a clinically meaningful difference of MPG (0.167 mmol/L), MAGE (0.072 mmol/L), and AUC24 (13.889 mmol/L·h) between LF-HC and HF-LC diets varied among participants, and those with posterior probability >80% were identified as high-carbohydrate responders (n = 9) or high-fat responders (n = 6). Analyses of the Bayesian-aggregated n-of-1 trials among all participants showed a relatively low posterior probability of reaching a clinically meaningful difference of the 3 outcomes between LF-HC and HF-LC diets.

CONCLUSIONS

N-of-1 trials are feasible to characterize personal response to dietary intervention in young Chinese adults.

Keyto app and device versus WW app on weight loss and metabolic risk in adults with overweight or obesity: A randomized trial

OBJECTIVE

The aim of this study was to determine whether a Mediterranean-style, ketogenic diet mobile health application (app) with breath acetone biofeedback is superior to a calorie-restricted, low-fat diet app in promoting weight loss.

METHODS

Participants (n = 155) with overweight/obesity (mean [SD]: age 41 [11] years, BMI = 34 [5] kg/m² , 71% female) were randomized to one of the interventions delivered entirely via app. Participants received a wireless scale and were instructed to take daily weight measurements. A third-party laboratory collected blood samples at baseline and 12 weeks.

RESULTS

Weight loss at 12 weeks was greater in the ketogenic (-5.6 kg; 95% CI: -6.7 kg to -4.5 kg) compared with the low-fat group (-2.5 kg; 95% CI: -3.6 kg to -1.4 kg) (between-group difference: -3.1 kg; 95% CI: -4.6 kg to -1.5 kg; p < 0.001). Weight loss at 24 weeks indicated durability of the effect (between-group difference: -5.5 kg; 95% CI: -8.3 kg to -2.8 kg; p < 0.001). Secondary/exploratory outcomes of hemoglobin A1c and liver enzymes were improved to a greater extent in the ketogenic diet group (p < 0.01).

CONCLUSIONS

Among adults with overweight/obesity, a ketogenic diet app with breath acetone biofeedback was superior to a calorie-restricted diet app at promoting weight loss in a real-world setting.

Benefits of Low Carbohydrate Diets: a Settled Question or Still Controversial?

PURPOSE OF REVIEW

The purpose of this review was to provide an update on the available data on the benefits of low-carbohydrate (low-carb) diets for weight management and type 2 diabetes (T2DM) and determine if low-carb diets were a settled question or still controversial.

RECENT FINDINGS

Most of the recent published literature in this area consists of reviews of past trials, with a relatively smaller number of recent trials. Low-carb is most commonly compared to low-fat, with problematically inconsistent definitions of both. There are numerous challenges in trying to draw clear conclusions about efficacy and effectiveness. Short-term vs. long-term effects can differ, which is likely impacted by adherence. Adherence is very different between metabolic chamber or feeding studies vs. free-living. Body weight alone is a crude measure that fails to capture potentially important differences in lean-mass, fat-mass, and body water. Benefits for glycemic control need to be balanced with impacts on non-glycemic outcomes such as LDL-cholesterol, the microbiome, and inflammation. It is important to differentiate between low-carb and very-low carbohydrate diets (VLCD). To date no large-scale long-term clinical trials have been conducted testing whether low-carb diets can prevent T2DM. Many issues regarding benefits and risks of low-carb diets remain controversial or unresolved, particularly for VLCD. Some of the recent, better studies highlighted in this review suggest strategies for resolving these controversies.

Novel dietary interventions for adolescents with obesity: A narrative review

Adolescent obesity is increasing and a range of treatment approaches are needed. Provision of tailored treatment options accounting for individual and family needs, preferences, and capacity may encourage adolescents with obesity to seek treatment, and/or improve treatment outcomes. Delivered by trained health care professionals, novel dietary interventions may have utility for adolescents not responding to conventional diets, adolescents with comorbidities or severe obesity, and/or when rapid or substantial weight loss is required. This review describes current evidence and clinical considerations relating to the use of very low energy diets, low carbohydrate diets, and intermittent energy restriction in the treatment of adolescent obesity. Emerging evidence on the use of these novel dietary interventions demonstrates short-term weight-related and cardiometabolic improvements. While the evidence is encouraging, and no serious adverse effects have been reported, monitoring of intervention safety is essential. Considerations for health care professionals providing care to adolescents include nutritional adequacy, psychosocial health and social relationships during the intervention. Furthermore, long-term weight-related, cardiometabolic and psychological health outcomes of these dietary interventions are not well understood. Large randomised controlled trials are warranted to inform clinical practice and future guidelines for the use of novel dietary interventions in adolescents with obesity.

The Carbohydrate Threshold in Pregnancy and Gestational Diabetes: How Low Can We Go?

The original nutrition approach for the treatment of gestational diabetes mellitus (GDM) was to reduce total carbohydrate intake to 33–40% of total energy (EI) to decrease fetal overgrowth. Conversely, accumulating evidence suggests that higher carbohydrate intakes (60–70% EI, higher quality carbohydrates with low glycemic index/low added sugars) can control maternal glycemia. The Institute of Medicine (IOM) recommends ≥175 g/d of carbohydrate intake during pregnancy; however, many women are consuming lower carbohydrate (LC) diets (<175 g/d of carbohydrate or <40% of EI) within pregnancy and the periconceptual period aiming to improve glycemic control and pregnancy outcomes. This report systematically evaluates recent data (2018–2020) to identify the LC threshold in pregnancy in relation to safety considerations. Evidence from 11 reports suggests an optimal carbohydrate range of 47–70% EI supports normal fetal growth; higher than the conventionally recognized LC threshold. However, inadequate total maternal EI, which independently slows fetal growth was a frequent confounder across studies. Effects of a carbohydrate intake <175 g/d on maternal ketonemia and plasma triglyceride/free fatty acid concentrations remain unclear. A recent randomized controlled trial (RCT) suggests a higher risk for micronutrient deficiency with carbohydrate intake ≤165 g/d in GDM. Well-controlled prospective RCTs comparing LC (<165 g/d) and higher carbohydrate energy-balanced diets in pregnant women are clearly overdue.

Methodological Quality of Systematic Reviews and Meta-Analysis on Asthma Treatments. A Cross-Sectional Study

Rationale: Systematic reviews (SRs) provide the best evidence of the effectiveness of treatment strategies for asthma. Carefully conducted SRs provide high-quality evidence for supporting decision-making, but the trustworthiness of conclusions can be hampered by limitation in rigor.Objectives: To appraise the methodological quality of a representative sample of SRs on asthma treatments in a cross-sectional study.Methods: A cross-sectional study was conducted to identify SRs on asthma treatment published between 2013 and 2019 by searching the Cochrane Database of Systematic Reviews, Embase, MEDLINE, and PsycINFO. SRs including at least one meta-analysis on asthma treatments were included. Methodological quality of included SRs was assessed with the Assessing the Methodological Quality of Systematic Reviews 2 instrument. Factors associated with methodological quality were explored using multivariate regression analysis.Results: One hundred thirty-six SRs were included and appraised, with a majority being non-Cochrane reviews (71.3%). Only 12 (8.8%) were of high overall quality; 9 (6.6%), 32 (23.5%), and 83 (61.0%) were of moderate, low, and critically low overall quality, respectively. More specifically, no SRs (0.0%) conducted a comprehensive literature search; only 3 (2.2%) justified why a particular primary study design was selected; 37 (27.2%) reported sources of funding among included studies; and 54 (39.7%) provided lists of excluded studies with justification. Cochrane reviews (adjusted odds ratio, 36.56; 95% confidence interval, 10.49-127.42) and SRs published after 2017 (adjusted odds ratio, 4.52; 95% confidence interval, 1.73-11.83) were positively associated with higher methodological quality.Conclusions: Methodological quality of SRs on asthma treatments are suboptimal. Future SRs should be improved by conducting comprehensive literature searches, justifying study design selection, providing a list of excluded studies, and reporting funding sources of included studies.

Mechanical, sensory, and consumer evaluation of ketogenic, gluten-free breads

Ketogenic, gluten-free breads comprised of almond flour, oat bran fiber, or combinations of both were compared. The textural properties, sensory attributes, and consumer acceptance were analyzed on each bread containing 100% almond flour (AF), 66.7% almond flour with 33.3% oat bran fiber (AOB), 66.7% oat bran fiber with 33.3% almond flour (OBA), and 100% oat bran fiber (OB). AF and AOB breads had a more open crumb structure composed of cells between 1-4 mm2. OBA and OB had a significantly dense crumb pattern made up of more cells less than one millimeter squared. Quantitative-descriptive analysis (QDA) and consumer acceptance testing was conducted 24 hr after baking and mechanical endpoints were evaluated 24, 72, and 120 hr after baking. AF and AOB breads were preferred over OBA and OB breads in QDA evaluation and consumer acceptance scores. Greater percentages of oat bran fiber resulted in a bread that was less moist, firmer in texture, and chewier with trained panelists. In both sensory evaluations, higher amounts of almond flour resulted in higher values in eggy flavor while increased amounts of oat bran fiber correlated with higher values in earthy flavor. Mechanical testing identified higher percentages of almond flour resulted in bread that was less firm and less chewy. Over time, all variations with almond flour became softer and less chewy, while the OB bread increased in firmness. Sensory cohesiveness did not correlate with the mechanical equivalent, identifying a need to re-evaluate the parameters used to calculate this objective endpoint.

Association of Carbohydrate and Fat Intake with Prevalence of Metabolic Syndrome Can Be Modified by Physical Activity and Physical Environment in Ecuadorian Adults: The ENSANUT-ECU Study

The associations of lifestyle and environment with metabolic syndrome (MetS) and cardiovascular disease have recently resulted in increased attention in research. This study aimed to examine interactive associations among carbohydrate and fat intake, physical environment (i.e., elevation and humidity), lifestyle, and MetS among Ecuadorian adults. We used data from the Ecuador National Health and Nutrition Survey 2012 (ENSANUT-ECU), with a total of 6023 participants aged 20 to 60 years included in this study. Logistic regression was used to determine the association of status of carbohydrate and fat intake, low-carbohydrate high-fat diet (LCHF) and medium-carbohydrate and fat (MCF) diet with MetS, where the high-carbohydrate low-fat (HCLF) diet was used as a reference. Women with LCHF and MCF diets showed lower prevalence of increased blood pressure (OR = 0.34, 95% CI: 0.19–0.59; OR = 0.50, 95% CI: 0.32–0.79, respectively). Women with MCF diet also showed lower prevalence of elevated fasting glucose (OR = 0.58, 95% CI: 0.37–0.91). Moreover, there were negative associations between MetS and reduced HDL cholesterol in women with MCF diet residing in low relative humidity (OR = 0.66, 95% CI: 0.45–0.98) and in women with LCHF diet residing at a high elevation (OR = 0.37, 95% CI: 0.16–0.86). Additionally, higher prevalence of increased waist circumference was observed in men with both MFC and LCHF diets who were physically inactive (OR = 1.89, 95% CI: 1.12–3.20; OR = 2.34, 95% CI: 1.19–4.60, respectively) and residing in high relative humidity (OR = 1.90, 95% CI: 1.08–2.89; OR = 2.63, 95% CI: 1.32–5.28, respectively). Our findings suggest that LCHF intake is associated with lower blood pressure, while MCF intake is associated with lower blood pressure and fasting glucose in Ecuadorian women. Furthermore, the associations of carbohydrate and fat intake with prevalence of MetS can be modified by physical activity, relative humidity, and elevation. The obtained outcomes may provide useful information for health programs focusing on dietary intake and lifestyle according to physical environment of the population to promote health and prevent metabolic diseases.

Supporting people to implement a reduced carbohydrate diet: a qualitative study in family practice

INTRODUCTION

Much of the science behind dietary guidelines for risk reduction and chronic disease management is equivocal, and there are well-accepted uncertainties and complexities relating to diet in everyday life, as well as physiological processes. Guidelines have therefore stopped short of aligning with one particular approach, instead highlighting several evidence-based options. However, reduced carbohydrate, or 'low-carb', diets have increasing traction in the media and with patients, practitioners and the general public. This qualitative study examines healthcare practitioner (HCP) experiences of implementing a reduced carbohydrate diet.

METHODS

Semistructured, qualitative interviews were conducted with 19 HCPs in the UK family practice (including general practitioners, practice nurses and non-medical practitioners), recruited through a special interest forum, and social media. Data analysis employed social science theory and methods to produce key themes.

RESULTS

All participants self-identified as 'low-carb practitioners' who, over time, had introduced a specific focus around carbohydrate reduction into their work. They reported transformations in patients' metabolic markers, patient enthusiasm for the approach and renewed job satisfaction. Key themes highlight experiences of: (1) discovering low-carb as a new 'tool-in-the-box'; (2) promoting and supporting incremental low-carb experimentation; and (3) diverging from established dietary guidelines.

CONCLUSIONS

This study provides important experience-based evidence on a topical dietary intervention. Participants strongly advocated for the use of low-carb diets. The successes described draw attention to the need for pragmatic, formative evaluation of low-carb advice and support as a 'complex intervention' (alongside physiological research), to justify, challenge and/or shape low-carb intervention in clinical practice. The findings raise important questions about the contribution of particular care practices to the apparent success of low-carb. Social science analyses can elucidate how dietary intervention is carried out across different healthcare settings (eg, dietetics, endocrinology) and patient groups, how healthcare practices intersect with people's everyday self-management and how different forms of evidence are invoked and prioritised.

Bidirectional Associations between Restrained Eating and Body Mass Index in Middle Childhood

The nature of the association between dietary restraint and weight has been examined in adult samples, but much less is known about this relationship among children. The current study examined the transactional associations among restrained eating behavior and weight among boys and girls during middle childhood. Data for this study came from 263 children participating in the Families and Schools for Health Project (FiSH), a longitudinal study of the psychosocial correlates of childhood obesity. Participants were interviewed by trained researchers in their third- and fourth-grade year when they completed questionnaires and anthropometric assessments. Dietary restraint was assessed using the restrained eating subscale of the Dutch Eating Behavior Questionnaire (DEBQ), and weight was assessed using Body Mass Index z-scores (BMIz). Bidirectional associations between variables were examined using cross-lagged models controlling for children's sex, ethnicity, and weight in first grade. Results indicated that weight in grade 3 was related to greater dietary restraint in grade 4 (B = 0.20, p = 0.001), but dietary restraint in grade 3 was not associated with weight in grade 4 (B = 0.01, p = 0.64). Neither child sex nor race/ethnicity were associated with BMIz or dietary restraint at either time point. Findings from this study advance the existing limited understanding of eating behavior development among children and show that weight predicts increases in children's dietary restraint in middle childhood.

The methodological quality of individual participant data meta-analysis on intervention effects: systematic review

OBJECTIVE

To assess the methodological quality of individual participant data (IPD) meta-analysis and to identify areas for improvement.

DESIGN

Systematic review.

DATA SOURCES

Medline, Embase, and Cochrane Database of Systematic Reviews.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

Systematic reviews with IPD meta-analyses of randomised controlled trials on intervention effects published in English.

RESULTS

323 IPD meta-analyses covering 21 clinical areas and published between 1991 and 2019 were included: 270 (84%) were non-Cochrane reviews and 269 (84%) were published in journals with a high impact factor (top quarter). The IPD meta-analyses showed low compliance in using a satisfactory technique to assess the risk of bias of the included randomised controlled trials (43%, 95% confidence interval 38% to 48%), accounting for risk of bias when interpreting results (40%, 34% to 45%), providing a list of excluded studies with justifications (32%, 27% to 37%), establishing an a priori protocol (31%, 26% to 36%), prespecifying methods for assessing both the overall effects (44%, 39% to 50%) and the participant-intervention interactions (31%, 26% to 36%), assessing and considering the potential of publication bias (31%, 26% to 36%), and conducting a comprehensive literature search (19%, 15% to 23%). Up to 126 (39%) IPD meta-analyses failed to obtain IPD from 90% or more of eligible participants or trials, among which only 60 (48%) provided reasons and 21 (17%) undertook certain strategies to account for the unavailable IPD.

CONCLUSIONS

The methodological quality of IPD meta-analyses is unsatisfactory. Future IPD meta-analyses need to establish an a priori protocol with prespecified data syntheses plan, comprehensively search the literature, critically appraise included randomised controlled trials with appropriate technique, account for risk of bias during data analyses and interpretation, and account for unavailable IPD.

Carbohydrates: Separating fact from fiction

The role of carbohydrate in a healthy diet has been controversial. The confusion over carbohydrate has come from the long standing limitation of dietary recall studies as well as inability in many of these studies to delineate between the different types of carbohydrates. It is the aim of this paper, to understand and review the data on the role of carbohydrate as pertaining to weight, insulin resistance, diabetes, inflammation, lipids, as well as epidemiological data on long-term cardiovascular outcome and all-cause mortality. We have reviewed the latest epidemiological and intervention studies on fiber, whole grain, and refined carbohydrates on weight, diabetes, lipids as well as major adverse cardiac events that we deemed were scientifically rigorous. High intakes of dietary fiber and whole grains are associated with positive effects on metabolic health while diet high in sugar and refined carbohydrates have negative effects on cardiometabolic health. Consistent evidence indicates that low fat and low carbohydrate diets at comparable energy levels have similar effects on body weight. Large epidemiological studies show when carbohydrates are substituted for animal-derived fat or protein mortality increased while carbohydrate exchanged with plant based protein was associated with mortality reduction. Types of carbohydrate appear to be critical for mortality and cardiovascular events. Evidence shows that quality of the carbohydrate determine cardiometabolic health and cardiovascular events. Given that most people worldwide currently consume less than 20 g of dietary fiber per day with persistently high consumption of refined carbohydrates, current evidence emphasize the need for additional measures to increase the amount and the diversity of fiber intake for improvement of cardiometabolic and cardiovascular outcomes.

Scoping review of COVID-19-related systematic reviews and meta-analyses: can we really have confidence in their results?

Aim

The aim of this study was to systematically appraise the quality of a sample of COVID-19-related systematic reviews (SRs) and discuss internal validity threats affecting the COVID-19 body of evidence.

Design

We conducted a scoping review of the literature. SRs with or without meta-analysis (MA) that evaluated clinical data, outcomes or treatments for patients with COVID-19 were included.

Main outcome measures

We extracted quality characteristics guided by A Measurement Tool to Assess Systematic Reviews-2 to calculate a qualitative score. Complementary evaluation of the most prominent published limitations affecting the COVID-19 body of evidence was performed.

Results

A total of 63 SRs were included. The majority were judged as a critically low methodological quality. Most of the studies were not guided by a pre-established protocol (39, 62%). More than half (39, 62%) failed to address risk of bias when interpreting their results. A comprehensive literature search strategy was reported in most SRs (54, 86%). Appropriate use of statistical methods was evident in nearly all SRs with MAs (39, 95%). Only 16 (33%) studies recognised heterogeneity in the definition of severe COVID-19 as a limitation of the study, and 15 (24%) recognised repeated patient populations as a limitation.

Conclusion

The methodological and reporting quality of current COVID-19 SR is far from optimal. In addition, most of the current SRs fail to address relevant threats to their internal validity, including repeated patients and heterogeneity in the definition of severe COVID-19. Adherence to proper study design and peer-review practices must remain to mitigate current limitations.

Dietary interventions for obesity: clinical and mechanistic findings

Dietary modification is central to obesity treatment. Weight loss diets are available that include various permutations of energy restriction, macronutrients, foods, and dietary intake patterns. Caloric restriction is the common pathway for weight reduction, but different diets may induce weight loss by varied additional mechanisms, including by facilitating dietary adherence. This narrative Review of meta-analyses and select clinical trials found that lower-calorie diets, compared with higher-calorie regimens, reliably induced larger short-term (<6 months) weight losses, with deterioration of this benefit over the long term (>12 months). Few significant long-term differences in weight loss were observed for diets of varying macronutrient composition, although some regimens were found to have short-term advantages (e.g., low carbohydrate versus low fat). Progress in improving dietary adherence, which is critical to both short- and long-term weight loss, could result from greater efforts to identify behavioral and metabolic phenotypes among dieters.