Energy expenditure and body composition changes after an isocaloric ketogenic diet in overweight and obese men

The Impact of Different Nutritional Approaches on Body Composition in People Living with Obesity

PURPOSE OF REVIEW

This narrative review aimed to provide an overview of the current evidence on the impact of various nutritional strategies on body composition in people living with obesity (PLwO), with particular attention to fat mass (FM), fat-free mass (FFM), and fat distribution.

RECENT FINDINGS

Obesity is increasingly linked to cardiometabolic complications, yet common diagnostic metrics such as body mass index (BMI) do not capture changes in FM or FFM. Recent studies highlight the variable effects of different dietary interventions on body compartments. High-protein and ketogenic diets are associated with greater preservation of FFM and reductions in visceral adipose tissue (VAT), while the Mediterranean diet shows promise for long-term adherence and improvements in metabolic health. Intermittent fasting and time-restricted eating demonstrate efficacy in FM reduction but present mixed results regarding FFM retention and sustainability. Dietary strategies exert diverse effects on body composition in PLwO, underscoring the importance of tailoring interventions to individual metabolic profiles and health goals. Personalized nutrition approaches that prioritize the preservation of lean mass and reduction of VAT, along with sustainable adherence, are critical for optimizing obesity management beyond weight loss alone.

Anthropometric Trajectories and Dietary Compliance During a Personalized Ketogenic Program

BACKGROUND/OBJECTIVES

Ketogenic diets (KDs) have gained attention for their potential to promote weight loss and metabolic improvements. However, data on long-term body composition changes and adherence rates in real-world settings remain limited.

OBJECTIVE

This study aimed to assess the effects of a personalized ketogenic dietary program on anthropometric parameters over a 9-month period and to evaluate adherence across time.

METHODS

A total of 491 adults participated in a longitudinal intervention involving a structured ketogenic nutrition plan with follow-up at 3, 6, and 9 months. Body weight, fat mass (FM), skeletal muscle mass (SMM), and other composition metrics were measured at each visit.

RESULTS

Significant reductions in body weight (-12.6 kg) and fat mass (-10.3 kg) were observed after 3 months (p < 0.001), with minimal changes at 6 months and partial regain by Month 9. SMM remained relatively stable throughout the study. Retention dropped substantially after 3 months, dropping from 487 to 115 participants at Month 6 and 41 at Month 9. Despite this, participants who completed the program maintained significant anthropometric improvements.

CONCLUSIONS

A well-formulated ketogenic diet may promote rapid fat loss while preserving lean mass in the short term. However, long-term adherence poses significant challenges. Strategies to enhance dietary sustainability and retention are essential for maximizing the benefits of KDs in clinical practice.

Different action of glucocorticoid receptor in adipose tissue remodelling to modulate energy homeostasis by chronic restraint stress

BACKGROUND

Chronic stress in daily life is a well-known trigger for various health issues. Despite advancements in obesity research, the mechanisms governing lipid metabolism in adipose tissue during cachexia remain poorly understood.

METHODS

A chronic restraint stress (CRS) model was used to induce significant physiological and psychological stress in mice. Mice were subjected to 6 h of restraint daily in 50 mL plastic tubes for seven consecutive days. A fasting control group was included for comparison. Post-stress assessments included behavioural tests, glucose and insulin tolerance tests and indirect calorimetry. Blood and adipose tissue samples were collected for mRNA and protein analyses.

RESULTS

CRS induced significant psychological and physiological changes in mice, including depression-like behaviours, weight loss and reduced insulin sensitivity. Notably, CRS caused extensive adipose tissue remodelling. White adipose tissue (WAT) underwent significant 'browning' accompanied by an increase in the expression of thermogenic proteins. This counteracted the stress-induced 'whitening' of brown adipose tissue (BAT), which exhibited impaired thermogenesis and functionality, thereby maintaining energy balance systematically. The glucocorticoid receptor (GR) plays a crucial role in lipid metabolism regulation during these changes. GR expression levels were inversely correlated in BAT and WAT, but aligned with the expression patterns of thermogenic proteins across adipose tissues. These findings suggest that under chronic metabolic stress, GR mediates tissue-specific responses in adipose tissues, driving functional and phenotypic transitions in BAT and WAT to maintain energy homeostasis.

CONCLUSIONS

This study provides novel insights into the contrasting thermogenic phenotypes of BAT and WAT under emaciation and highlights the critical role of GRs in adipose tissue remodelling during CRS and its potential as a therapeutic target. Addressing GR-mediated changes in adipose tissues may help alleviate BAT dysfunction in cachexia and promote WAT browning, enhancing metabolic stress resistance.

Effects of Ketone Ester Supplementation on Cognition and Appetite in Individuals with and Without Metabolic syndrome: A Randomized Trial

There are currently no non-pharmacological solutions to combat the appetite and cognitive dysfunctions associated with metabolic syndrome (MetS). Ketosis may be a potential solution, though the restrictive nature of dietary ketosis limits its long-term utility. Oral administration of exogenous ketone esters (KE) independently induces ketosis, eliciting hyperketonemia without the need for prolonged dietary restrictions. However, the acute effects of oral KEs on appetite and cognition have not been evaluated in individuals with MetS. For this randomized, single-blind, placebo-controlled, matched-pairs crossover study, 10 individuals with MetS and 10 without (non-MetS) matched for age, sex, and race/ethnicity completed a cardiometabolic screening/familiarization visit and two experimental trials. During the experimental trials, cognitive function, subjective appetite, and respiratory gases were measured at baseline and for 2h following the ingestion of a randomly assigned KE or placebo drink. Post-trial food intake was also collected. Independent of MetS group, indices of working memory significantly improved (p ≤ .035), and blood glucose significantly decreased (p < .001), following KE ingestion. However, after the KE condition, markers of subjective appetite (p ≤ .048) only decreased in the non-MetS group. Post-trial relative fat intake was higher in the MetS group than the non-MetS group following the KE (p = .002), and lower after the KE than the placebo for the non-MetS group (p = .028). Our findings indicate that while cognitive function may increase following KE ingestion independent of MetS, appetite may only decrease in those without MetS; providing further insight to our understanding of the behavioral and metabolic responses to exogenous ketosis.

American society for preventive cardiology 2024 cardiovascular disease prevention: Highlights and key sessions

Groundbreaking strategies for preventive cardiology were showcased at the 2024 American Society for Preventive Cardiology (ASPC) Congress on Cardiovascular Disease (CVD) Prevention held in Salt Lake City, Utah, from August 2nd to 4th, 2024. The event featured 69 moderators and 13 scientific sessions comprised of 98 topics, 36 satellite events, 133 poster presentations, and 27 lifestyle classes. The conference highlighted innovative strategies focused on integrating cardiovascular, kidney, and metabolic health, presenting a cohesive approach for managing complex, interrelated conditions. Pivotal studies have addressed the role of lipid-lowering therapies, the benefits of early statin initiation, and the importance of precision medicine in preventing CVD. The ASPC's emphasis on translating this research into practical clinical tools has the potential to revolutionize preventive care strategies, making strides toward reducing the burden of CVD globally and improving long-term patient outcomes through personalized and early intervention approaches.

Effects of a 12 Week Ketogenic Diet Intervention on Obese and Overweight Females with Glucose and Lipid Metabolism Disturbance

BACKGROUND/OBJECTIVES

We evaluated the effects of a 12-week hypocaloric ketogenic diet (KD) on glucose and lipid metabolism, as well as body mass, in overweight, obese, and healthy-weight females. One hundred adult females completed the study, including 64 obese (97.99 ± 11.48 kg), 23 overweight (75.50 ± 5.12 kg), and 11 with normal body mass (65.93 ± 3.40 kg). All participants followed a KD consisting of less than 30 g of carbohydrates, approximately 60 g of protein, and 140 g of fat per day (80% unsaturated and 20% saturated fat).

METHODS

Glucose (Gl), insulin (I), glycated haemoglobin (HBA1c), HOMA-IR, triglycerides (TG), and high-density lipoprotein cholesterol (HDL-C) were measured before and after the intervention. Additionally, body mass (BM), BMI (Body Mass Index), waist circumference (WC), hip circumference (HC), and thigh circumference (TC) were recorded.

RESULTS

After 12 weeks of the KD, significant improvements were observed in GL, I, TG, HDL-C, HOMA-IR across all groups. Also BM, BMI, TC, WC, and HC were significantly reduced in all participants. Notably, obese participants showed greater reductions in all variables compared to overweight and healthy-weight females.

CONCLUSIONS

A 12-week KD led to more pronounced improvements in biochemical markers and body mass in obese females compared to other groups. A KD may be particularly beneficial for obese females with hyperglycaemia, hyperinsulinemia, and lipid profile disturbances.

Clinical research framework proposal for ketogenic metabolic therapy in glioblastoma

Glioblastoma (GBM) is the most aggressive primary brain tumor in adults, with a universally lethal prognosis despite maximal standard therapies. Here, we present a consensus treatment protocol based on the metabolic requirements of GBM cells for the two major fermentable fuels: glucose and glutamine. Glucose is a source of carbon and ATP synthesis for tumor growth through glycolysis, while glutamine provides nitrogen, carbon, and ATP synthesis through glutaminolysis. As no tumor can grow without anabolic substrates or energy, the simultaneous targeting of glycolysis and glutaminolysis is expected to reduce the proliferation of most if not all GBM cells. Ketogenic metabolic therapy (KMT) leverages diet-drug combinations that inhibit glycolysis, glutaminolysis, and growth signaling while shifting energy metabolism to therapeutic ketosis. The glucose-ketone index (GKI) is a standardized biomarker for assessing biological compliance, ideally via real-time monitoring. KMT aims to increase substrate competition and normalize the tumor microenvironment through GKI-adjusted ketogenic diets, calorie restriction, and fasting, while also targeting glycolytic and glutaminolytic flux using specific metabolic inhibitors. Non-fermentable fuels, such as ketone bodies, fatty acids, or lactate, are comparatively less efficient in supporting the long-term bioenergetic and biosynthetic demands of cancer cell proliferation. The proposed strategy may be implemented as a synergistic metabolic priming baseline in GBM as well as other tumors driven by glycolysis and glutaminolysis, regardless of their residual mitochondrial function. Suggested best practices are provided to guide future KMT research in metabolic oncology, offering a shared, evidence-driven framework for observational and interventional studies.

International society of sports nutrition position stand: ketogenic diets

POSITION STATEMENT

The International Society of Sports Nutrition (ISSN) provides an objective and critical review of the use of a ketogenic diet in healthy exercising adults, with a focus on exercise performance and body composition. However, this review does not address the use of exogenous ketone supplements. The following points summarize the position of the ISSN.

1. A ketogenic diet induces a state of nutritional ketosis, which is generally defined as serum ketone levels above 0.5 mM. While many factors can impact what amount of daily carbohydrate intake will result in these levels, a broad guideline is a daily dietary carbohydrate intake of less than 50 grams per day.

2. Nutritional ketosis achieved through carbohydrate restriction and a high dietary fat intake is not intrinsically harmful and should not be confused with ketoacidosis, a life-threatening condition most commonly seen in clinical populations and metabolic dysregulation.

3. A ketogenic diet has largely neutral or detrimental effects on athletic performance compared to a diet higher in carbohydrates and lower in fat, despite achieving significantly elevated levels of fat oxidation during exercise (~1.5 g/min).

4. The endurance effects of a ketogenic diet may be influenced by both training status and duration of the dietary intervention, but further research is necessary to elucidate these possibilities. All studies involving elite athletes showed a performance decrement from a ketogenic diet, all lasting six weeks or less. Of the two studies lasting more than six weeks, only one reported a statistically significant benefit of a ketogenic diet.

5. A ketogenic diet tends to have similar effects on maximal strength or strength gains from a resistance training program compared to a diet higher in carbohydrates. However, a minority of studies show superior effects of non-ketogenic comparators.

6. When compared to a diet higher in carbohydrates and lower in fat, a ketogenic diet may cause greater losses in body weight, fat mass, and fat-free mass, but may also heighten losses of lean tissue. However, this is likely due to differences in calorie and protein intake, as well as shifts in fluid balance.

7. There is insufficient evidence to determine if a ketogenic diet affects males and females differently. However, there is a strong mechanistic basis for sex differences to exist in response to a ketogenic diet.

Ketogenic diet in clinical populations-a narrative review

Ketogenic diet (KD) is a high-fat, low-carbohydrate (CHO) diet, designed to induce a metabolic state of ketosis in which the body metabolizes primarily lipids for energy production. Various forms of KD are being promoted as promising treatments for numerous health conditions from chronic headaches to weight-loss and even different forms of cancer and are becoming increasingly more popular. KD appears to be an efficacious approach for weight-loss, and maintenance, improved glycemia, cognitive function and cancer prognosis. However, there is a controversy regarding the safety of KD, and the potential health risks that might be associated with long-term exposure to KD. There is a gap between the acceptance and utilization of KD in individuals with health conditions and the criticism and negative attitudes toward KD by some clinicians. Many individuals choose to follow KD and are encouraged by the positive results they experience. Although the medical establishment does not endorse KD as a first line of treatment, clinicians need to be informed about KD, and offer support and medical supervision for patients who self-select to follow KD. This can ensure that within the boundaries of KD, patients will make good and healthy dietary choices and prevent clinical disengagement in extreme cases. To that end, there is an urgent need for good quality research to address the issues of long-term safety of KD in different clinical populations and for standardization of KD both in research and in the clinic.

Ketogenic Diet: A Review of Composition Diversity, Mechanism of Action and Clinical Application

The ketogenic diet (KD) is a special high-fat, very low-carbohydrate diet with the amount of protein adjusted to one's requirements. By lowering the supply of carbohydrates, this diet induces a considerable change in metabolism (of protein and fat) and increases the production of ketone bodies. The purpose of this article is to review the diversity of composition, mechanism of action, clinical application and risk associated with the KD. In the last decade, more and more results of the diet's effects on obesity, diabetes and neurological disorders, among other examples have appeared. The beneficial effects of the KD on neurological diseases are related to the reconstruction of myelin sheaths of neurons, reduction of neuron inflammation, decreased production of reactive oxygen species, support of dopamine production, repair of damaged mitochondria and formation of new ones. Minimizing the intake of carbohydrates results in the reduced absorption of simple sugars, thereby decreasing blood glucose levels and fluctuations of glycaemia in diabetes. Studies on obesity indicate an advantage of the KD over other diets in terms of weight loss. This may be due to the upregulation of the biological activity of appetite-controlling hormones, or to decreased lipogenesis, intensified lipolysis and increased metabolic costs of gluconeogenesis. However, it is important to be aware of the side effects of the KD. These include disorders of the digestive system as well as headaches, irritability, fatigue, the occurrence of vitamin and mineral deficiencies and worsened lipid profile. Further studies aimed to determine long-term effects of the KD are required.

Recommendations for Designing, Conducting, and Reporting Feeding Trials in Nutrition Research

Double-blind, placebo-controlled, randomized controlled trials are the gold standard for clinical trials in nutrition science. For trials of whole diets, dietary counseling is advantageous as they offer clinical translatability although can vary in the fidelity of the intended intervention from participant to participant and across studies. Feeding trials, in which most or all food is provided, offer high precision and can provide proof-of-concept evidence that a dietary intervention is efficacious and can also better evaluate the effect of known quantities of foods and nutrients on physiology. However, they come with additional methodological complexities. Feeding trials also call for a variety of unique methodological considerations, not least of which relate to the design and delivery of diets to participants. This review aims to provide a comprehensive summary of recommendations for design and conduct of feeding trials, encompassing domiciled and nondomiciled feeding trials. Several pertinent aspects of trial design and methodology are discussed, including defining the study population to maximize retention, safety, and generalizability of findings, recommendations for design of control interventions and optimizing blinding, and specific considerations for clinical populations. A detailed stepwise process for menu design, development, validation, and delivery are also presented. These recommendations aim to facilitate methodologic consistency and execution of high-quality feeding trials, ultimately facilitating improved understanding of the role of diet in treating disease and the underpinning mechanisms.

Diet order significantly affects energy balance for diets varying in macronutrients but not ultraprocessing in crossover studies without a washout period

BACKGROUND

Crossover studies can induce order effects, especially when they lack a washout period.

OBJECTIVES

We performed secondary analyses comparing groups of subjects randomly assigned to different diet orders in 2 inpatient crossover studies originally designed to compare within-subject differences in ad libitum energy intake. One study compared minimally processed low-carbohydrate (LC) compared with low-fat (LF) diets, and the other matched macronutrients and compared minimally processed food (MPF) with ultraprocessed food (UPF) diets.

METHODS

Diet order group comparisons of changes in body weight and body composition, and differences in energy expenditure and food intake were assessed over 4 wk in 20 adults randomly assigned to either the LC followed immediately by the LF diet (LC → LF) or the opposite order (LF → LC), and 20 adults randomly assigned to either the MPF followed by the UPF (MPF → UPF) diets or the opposite order (UPF → MPF).

RESULTS

Subjects randomly assigned to LC → LF lost 2.9 ± 1.1 kg more body weight (P <0.001) and 1.5 ± 0.6 kg more body fat (P = 0.03) than the LF → LC group, likely because the LC → LF group consumed 921 ± 304 kcal/d less than the LF → LC group (P = 0.003). These energy intake differences were driven by the last 2 wk (-1610 ± 312 kcal/d; P < 0.0001), perhaps because of carryover effects of gut adaptations during the first 2 wk arising from large differences in the mass of food (1296 ± 215 g/d; P <0.00001) and fiber consumed (58 ± 6 g/d; P <0.00001). There were no significant diet order effects on energy intake, body weight, or body composition changes between UPF → MPF and MPF → UPF groups.

CONCLUSIONS

Diet order significantly affected energy intake, body weight, and body fat in a 4-wk crossover inpatient diet study varying in macronutrients, but not in a similarly structured study varying in ultraprocessed foods. This trial was registered at clinicaltrials.gov as NCT03407053 and NCT03878108.

Gut-derived appetite hormones do not explain energy intake differences in humans following low-carbohydrate versus low-fat diets

OBJECTIVE

The objective of this study was to explore how dietary macronutrient composition influences postprandial appetite hormone responses and subsequent energy intake.

METHODS

A total of 20 adults (mean [SEM], age 30 [1] years, BMI 27.8 [1.3] kg/m2, n = 8 with normal weight, n = 6 with overweight, n = 6 with obesity) consumed a low-fat (LF) diet (10% fat, 75% carbohydrate) and a low-carbohydrate (LC) diet (10% carbohydrate, 75% fat) for 2 weeks each in an inpatient randomized crossover design. At the end of each diet, participants consumed isocaloric macronutrient-representative breakfast test meals, and 6-h postprandial responses were measured. Ad libitum energy intake was measured for the rest of the day.

RESULTS

The LC meal resulted in greater mean postprandial plasma active glucagon-like peptide-1 (GLP-1; LC: 6.44 [0.78] pg/mL, LF: 2.46 [0.26] pg/mL; p < 0.0001), total glucose-dependent insulinotropic polypeptide (GIP; LC: 578 [60] pg/mL, LF: 319 [37] pg/mL; p = 0.0004), and peptide YY (PYY; LC: 65.6 [5.6] pg/mL, LF: 50.7 [3.8] pg/mL; p = 0.02), whereas total ghrelin (LC: 184 [25] pg/mL, LF: 261 [47] pg/mL; p = 0.0009), active ghrelin (LC: 91 [9] pg/mL, LF: 232 [28] pg/mL; p < 0.0001), and leptin (LC: 26.9 [6.5] ng/mL, LF: 35.2 [7.5] ng/mL; p = 0.01) were lower compared with LF. Participants ate more during LC at lunch (244 [85] kcal; p = 0.01) and dinner (193 [86] kcal; p = 0.04), increasing total subsequent energy intake for the day compared with LF (551 [103] kcal; p < 0.0001).

CONCLUSIONS

In the short term, endogenous gut-derived appetite hormones do not necessarily determine ad libitum energy intake.

Exercise-Induced cytokines, diet, and inflammation and their role in adipose tissue metabolism

BACKGROUND

Obesity poses a significant global health challenge, necessitating effective prevention and treatment strategies. Exercise and diet are recognized as pivotal interventions in combating obesity. This study reviews the literature concerning the impact of exercise-induced cytokines, dietary factors, and inflammation on adipose tissue metabolism, shedding light on potential pathways for therapeutic intervention.

METHODOLOGY

A comprehensive review of relevant literature was conducted to elucidate the role of exercise-induced cytokines, including interleukin-6 (IL-6), interleukin-15 (IL-15), brain-derived neurotrophic factor (BDNF), irisin, myostatin, fibroblast growth factor 21 (FGF21), follistatin (FST), and angiopoietin-like 4 (ANGPTL4), in adipose tissue metabolism. Various databases were systematically searched using predefined search terms to identify relevant studies. Articles selected for inclusion underwent thorough analysis to extract pertinent data on the mechanisms underlying the influence of these cytokines on adipose tissue metabolism.

RESULTS AND DISCUSSION

Exercise-induced cytokines exert profound effects on adipose tissue metabolism, influencing energy expenditure (EE), thermogenesis, fat loss, and adipogenesis. For instance, IL-6 activates AMP-activated protein kinase (AMPK), promoting fatty acid oxidation and reducing lipogenesis. IL-15 upregulates peroxisome proliferator-activated receptor delta (PPARδ), stimulating fatty acid catabolism and suppressing lipogenesis. BDNF enhances AMPK-dependent fat oxidation, while irisin induces the browning of white adipose tissue (WAT), augmenting thermogenesis. Moreover, myostatin, FGF21, FST, and ANGPTL4 each play distinct roles in modulating adipose tissue metabolism, impacting factors such as fatty acid oxidation, adipogenesis, and lipid uptake. The elucidation of these pathways offers valuable insights into the complex interplay between exercise, cytokines, and adipose tissue metabolism, thereby informing the development of targeted obesity management strategies.

CONCLUSION

Understanding the mechanisms by which exercise-induced cytokines regulate adipose tissue metabolism is critical for devising effective obesity prevention and treatment modalities. Harnessing the therapeutic potential of exercise-induced cytokines, in conjunction with dietary interventions, holds promise for mitigating the global burden of obesity. Further research is warranted to delineate the precise mechanisms underlying the interactions between exercise, cytokines, and adipose tissue metabolism.

Energy Expenditure in Humans: Principles, Methods, and Changes Throughout the Life Course

Humans require energy to sustain their daily activities throughout their lives. This narrative review aims to (a) summarize principles and methods for studying human energy expenditure, (b) discuss the main determinants of energy expenditure, and (c) discuss the changes in energy expenditure throughout the human life course. Total daily energy expenditure is mainly composed of resting energy expenditure, physical activity energy expenditure, and the thermic effect of food. Total daily energy expenditure and its components are estimated using variations of the indirect calorimetry method. The relative contributions of organs and tissues determine the energy expenditure under different physiological conditions. Evidence shows that energy expenditure varies along the human life course, at least in part due to changes in body composition, the mass and specific metabolic rates of organs and tissues, and levels of physical activity. This information is crucial to estimate human energy requirements for maintaining health throughout the life course.

24-h energy expenditure in people with type 1 diabetes: impact on equations for clinical estimation of energy expenditure

BACKGROUND/OBJECTIVES

Type 1 diabetes (T1D) is associated with an increase in resting metabolic rate (RMR), but the impact of T1D on other components of 24-h energy expenditure (24-h EE) is not known. Also, there is a lack of equations to estimate 24-h EE in patients with T1D. The aims of this analysis were to compare 24-h EE and its components in young adults with T1D and healthy controls across the spectrum of body mass index (BMI) and derive T1D-specific equations from clinical variables.

SUBJECTS/METHODS

Thirty-three young adults with T1D diagnosed ≥1 year prior and 33 healthy controls matched for sex, age and BMI were included in this analysis. We measured 24-h EE inside a whole room indirect calorimeter (WRIC) and body composition with dual x-ray absorptiometry.

RESULTS

Participants with T1D had significantly higher 24-h EE than healthy controls (T1D = 2047 ± 23 kcal/day vs control= 1908 ± 23 kcal/day; P < 0.01). We derived equations to estimate 24-h EE with both body composition (fat free mass + fat mass) and anthropometric (weight + height) models, which provided high coefficients of determination (R2 = 0.912 for both). A clinical model that did not incorporate spontaneous physical activity yielded high coefficients of determination as well (R2 = 0.897 and R2 = 0.880 for body composition and anthropometric models, respectively).

CONCLUSION

These results confirm that young adults with established T1D have increased 24-h EE relative to controls without T1D. The derived equations from clinically available variables can assist clinicians with energy prescriptions for weight management in patients with T1D.

The use of accelerometers to improve estimation of the thermic effect of food in whole room calorimetry studies

We tested whether spontaneous physical activity (SPA) from accelerometers could be used in a whole room calorimeter to estimate thermic effect of food (TEF). Eleven healthy participants (n = 7 females; age: 27 ± 4 yr; body mass index: 22.8 ± 2.6 kg/m2) completed two 23-h visits in randomized order: one "fed" with meals provided and one "fasted" with no food. SPA was measured by ActivPAL and Actigraph accelerometers. Criterion TEF was calculated as the difference in total daily energy expenditure (TDEE) between fed and fasted visits and compared with three methods of estimating TEF: 1) SPA-adjusted TEF (adjTEF)-difference in TDEE without SPA between visits, 2) Wakeful TEF-difference in energy expenditure obtained from linear regression and basal metabolic rate during waking hours, 3) 24-h TEF-increase in TDEE above SPA and sleeping metabolic rate. Criterion TEF was 9.4 ± 4.5% of TDEE. AdjTEF (difference in estimated vs. criterion TEF: activPAL: -0.3 ± 3.3%; Actigraph: -1.8 ± 8.0%) and wakeful TEF (activPAL: -0.9 ± 6.1%; Actigraph: -2.8 ± 7.6%) derived from both accelerometers did not differ from criterion TEF (all P > 0.05). ActivPAL-derived 24-h TEF overestimated TEF (6.8 ± 5.4%, P = 0.002), whereas Actigraph-derived 24-h TEF was not significantly different (4.3 ± 9.4%, P = 0.156). TEF estimations using activPAL tended to show better individual-level agreement (i.e., smaller coefficients of variation). Both accelerometers can be used to estimate TEF in a whole room calorimeter; wakeful TEF using activPAL is the most viable option given strong group-level accuracy and reasonable individual agreement.NEW & NOTEWORTHY Two research-grade accelerometers can effectively estimate spontaneous physical activity and improve the estimation of thermic effect of food (TEF) in whole room calorimeters. The activPAL demonstrates strong group-level accuracy and reasonable individual-level agreement in estimating wakeful TEF, whereas a hip-worn Actigraph is an acceptable approach for estimating 24-h TEF. These results highlight the promising potential of accelerometers in advancing energy balance research by improving the assessment of TEF within whole room calorimeters.

Ketogenic diet-induced bile acids protect against obesity through reduced calorie absorption

The low-carbohydrate ketogenic diet (KD) has long been practiced for weight loss, but the underlying mechanisms remain elusive. Gut microbiota and metabolites have been suggested to mediate the metabolic changes caused by KD consumption, although the particular gut microbes or metabolites involved are unclear. Here, we show that KD consumption enhances serum levels of taurodeoxycholic acid (TDCA) and tauroursodeoxycholic acid (TUDCA) in mice to decrease body weight and fasting glucose levels. Mechanistically, KD feeding decreases the abundance of a bile salt hydrolase (BSH)-coding gut bacterium, Lactobacillus murinus ASF361. The reduction of L. murinus ASF361 or inhibition of BSH activity increases the circulating levels of TDCA and TUDCA, thereby reducing energy absorption by inhibiting intestinal carbonic anhydrase 1 expression, which leads to weight loss. TDCA and TUDCA treatments have been found to protect against obesity and its complications in multiple mouse models. Additionally, the associations among the abovementioned bile acids, microbial BSH and metabolic traits were consistently observed both in an observational study of healthy human participants (n = 416) and in a low-carbohydrate KD interventional study of participants who were either overweight or with obesity (n = 25). In summary, we uncover a unique host-gut microbiota metabolic interaction mechanism for KD consumption to decrease body weight and fasting glucose levels. Our findings support TDCA and TUDCA as two promising drug candidates for obesity and its complications in addition to a KD.

Effects of a Ketogenic Diet on Body Composition in Healthy, Young, Normal-Weight Women: A Randomized Controlled Feeding Trial

This study investigates the effects of a ketogenic low-carbohydrate high-fat (LCHF) diet on body composition in healthy, young, normal-weight women. With the increasing interest in ketogenic diets for their various health benefits, this research aims to understand their impact on body composition, focusing on women who are often underrepresented in such studies. Conducting a randomized controlled feeding trial with a crossover design, this study compares a ketogenic LCHF diet to a Swedish National Food Agency (NFA)-recommended control diet over four weeks. Seventeen healthy, young, normal-weight women adhered strictly to the provided diets, with ketosis confirmed through blood β-hydroxybutyrate concentrations. Dual-energy X-ray absorptiometry (DXA) was utilized for precise body composition measurements. To avoid bias, all statistical analyses were performed blind. The findings reveal that the ketogenic LCHF diet led to a significant reduction in both lean mass (-1.45 kg 95% CI: [-1.90;-1.00]; p < 0.001) and fat mass (-0.66 kg 95% CI: [-1.00;-0.32]; p < 0.001) compared to the control diet, despite similar energy intake and physical activity levels. This study concludes that while the ketogenic LCHF diet is effective for weight loss, it disproportionately reduces lean mass over fat mass, suggesting the need for concurrent strength training to mitigate muscle loss in women following this diet.

Relationships between oral function, dietary intake and nutritional status in older adults aged 75 years and above: a cross-sectional study

BACKGROUND

Malnutrition is related to impaired oral health and function that causes poor dietary intake, declining the general health of older adults. The role of dietary intake in the association between oral function and nutritional status of Chinese older adults (aged 75 and above) was examined in this cross-sectional study.

METHODS

Through the randomized cluster sampling method, 267 older adults living in rural areas of Qingdao, Shandong (aged 81.4 ± 4.3, 75-94 years) were chosen as the primary research participants. A Mini Nutritional Assessment - Short Form was used to determine nutritional status, and Food Frequency Questionnaire and 24-hour Food Intake Recall were used to assess dietary intake. The oral function was evaluated by analyzing the teeth, oral problems, bite force, tongue pressure, lip sealing pressure, chewing function questionnaire, whole saliva flow rate, 10-Item Eating Assessment Tool, and water swallow test.

RESULTS

Based on the MNA-SF score, it was divided into a well-nourished group and a malnutrition group, with the malnutrition group comprising 40.6% of participants. The participants in the malnutrition group showed a higher rate of xerostomia, lower bite force, tongue pressure, and lip sealing pressure, and higher Chewing Function Questionnaire and 10-Item Eating Assessment Tool scores. Furthermore, their plant fat, iron, cereals and potatoes, vegetables, fruits, and seafood intake were relatively low. The regression model indicated that exercise frequency, stroke, chewing and swallowing function, intake of vegetables and fruits were risk factors for nutritional status of older adults.

CONCLUSION

Malnutrition was relatively common among the Chinese older adults aged 75 and above, and it was significantly correlated with exercise frequency, stroke, chewing and swallowing function, and intake of vegetables and fruits. Therefore, nutrition management should be carried out under the understanding and guidance of the oral function and dietary intake of the older adults.

Modelling remission from overweight type 2 diabetes reveals how altering advice may counter relapse

The development or remission of diet-induced overweight type 2 diabetes involves many biological changes which occur over very different timescales. Remission, defined by HbA1c<6.5%, or fasting plasma glucose concentration G<126 mg/dl, may be achieved rapidly by following weight loss guidelines. However, remission is often short-term, followed by relapse. Mathematical modelling provides a way of investigating a typical situation, in which patients are advised to lose weight and then maintain fat mass, a slow variable. Remission followed by relapse, in a modelling sense, is equivalent to changing from a remission trajectory with steady state G<126 mg/dl, to a relapse trajectory with steady state G≥126 mg/dl. Modelling predicts that a trajectory which maintains weight will be a relapse trajectory, if the fat mass chosen is too high, the threshold being dependent on the lipid to carbohydrate ratio of the diet. Modelling takes into account the effects of hepatic and pancreatic lipid on hepatic insulin sensitivity and β-cell function, respectively. This study leads to the suggestion that type 2 diabetes remission guidelines be given in terms of model parameters, not variables; that is, the patient should adhere to a given nutrition and exercise plan, rather than achieve a certain subset of variable values. The model predicts that calorie restriction, not weight loss, initiates remission from type 2 diabetes; and that advice of the form 'adhere to the diet and exercise plan' rather than 'achieve a certain weight loss' may help counter relapse.

Obesity: current state of the problem, multidisciplinary approach. (based on the consensus of the World Gastroenterological Organization “Obesity 2023” and the European guideline on obesity care in patients with gastrointestinal and liver diseases, 2022)

Obesity is the largest pandemic in the world, and its prevalence continues to increase. The purpose of the presented publication is to raise awareness of doctors about modern methods of diagnosing obesity and approaches to therapy, using an interdisciplinary team approach similar to that used in other chronic diseases, such as diabetes, heart disease and cancer. The article presents data from the World Gastroenterological Organization (2023) and the European Guidelines for the Treatment of Obesity in patients with diseases of the gastrointestinal tract and liver (2022). According to modern approaches, obesity should be considered as a chronic recurrent progressive disease, the treatment of which requires a comprehensive interdisciplinary approach involving psychologists and psychiatrists, nutritionists/nutritionists, therapists, endoscopists and surgeons, including lifestyle changes, a well-defined diet and exercise regimen, drug therapy, endoscopic or surgical methods of treatment. Conclusions. In order to stop the growing wave of obesity and its many complications and costs, doctors, insurance companies and health authorities should make systematic efforts to raise public awareness of both the adverse health risks associated with obesity and the potential reduction of risks through a comprehensive approach to therapy.

What could be the reasons for not losing weight even after following a weight loss program?

INTRODUCTION

Approximately four million people worldwide die annually because of obesity. Weight loss is commonly recommended as a first-line therapy in overweight and obese patients. Although many individuals attempt to lose weight, not everyone achieves optimal success. Few studies point out that weight loss eventually slows down, stagnates or reverses in 85% of the cases.

RESEARCH QUESTION

What could be the reasons for not losing weight even after following a weight loss program?

METHODS

A scoping review of the literature was performed using weight loss-related search terms such as 'Obesity,' 'Overweight,' 'Lifestyle,' 'weight loss,' 'Basal Metabolism,' 'physical activity,' 'adherence,' 'energy balance,' 'Sleep' and 'adaptations. The search involved reference tracking and database and web searches (PUBMED, Science Direct, Elsevier, Web of Science and Google Scholar). Original articles and review papers on weight loss involving human participants and adults aged > 18 years were selected. Approximately 231 articles were reviewed, and 185 were included based on the inclusion criteria.

DESIGN

Scoping review.

RESULTS

In this review, the factors associated with not losing weight have broadly been divided into five categories. Studies highlighting each subfactor were critically reviewed and discussed. A wide degree of interindividual variability in weight loss is common in studies even after controlling for variables such as adherence, sex, physical activity and baseline weight. In addition to these variables, variations in factors such as previous weight loss attempts, sleep habits, meal timings and medications can play a crucial role in upregulating or downregulating the association between energy deficit and weight loss results.

CONCLUSION

This review identifies and clarifies the role of several factors that may hinder weight loss after the exploration of existing evidence. Judging the effectiveness of respective lifestyle interventions by simply observing the 'general behavior of the groups' is not always applicable in clinical practice. Each individual must be monitored and advised as per their requirements and challenges.

Does Wrist-Worn Accelerometer Wear Compliance Wane over a Free-Living Assessment Period? An NHANES Analysis

PURPOSE

Accelerometers are used to objectively measure physical behaviors in free-living environments, typically for seven consecutive days or more. We examined whether participants experience "wear fatigue," a decline in wear time day over day, during typical assessment period acquired in a nationally representative sample of 6- to 80-yr-olds in the United States.

METHODS

Participants were instructed to wear an ActiGraph GT3X+ on their nondominant wrist continuously for seven consecutive days. Participants with seven complete days of recorded data, regardless of wear status, were included in the analyses ( N = 13,649). Wear was scored with the sleep, wake, and nonwear algorithm.

RESULTS

Participants averaged 1248 ± 3.6 min·d -1 (mean ± SE) of wear over the assessment, but wear time linearly decreased from day 1 (1295 ± 3.2 min) to day 7 (1170 ± 5.3 min), resulting in a wear fatigue of -18.1 ± 0.7 min·d -1 ( β ± SE). Wear fatigue did not differ by sex but varied by age-group-highest in adolescents (-26.8 ± 2.4 min·d -1 ) and lowest in older adults (-9.3 ± 0.9 min·d -1 ). Wear was lower in evening (1800-2359 h) and early morning (0000-0559 h) compared with the middle of the day and on weekend days compared with weekdays. We verified similar wear fatigue (-23.5 ± 0.7 min·d -1 ) in a separate sample ( N = 14,631) with hip-worn devices and different wear scoring. Applying minimum wear criteria of ≥10 h·d -1 for ≥4 d reduced wear fatigue to -5.3 and -18.7 min·d -1 for the wrist and hip, respectively.

CONCLUSIONS

Patterns of wear suggest noncompliance may disproportionately affect estimates of sleep and sedentary behavior, particularly for adolescents. Further study is needed to determine the effect of wear fatigue on longer assessments.

The therapeutic potential of ketones in cardiometabolic disease: impact on heart and skeletal muscle

β-Hydroxybutyrate (βOHB) is the major ketone in the body, and it is recognized as a metabolic energy source and an important signaling molecule. While ketone oxidation is essential in the brain during prolonged fasting/starvation, other organs such as skeletal muscle and the heart also use ketones as metabolic substrates. Additionally, βOHB-mediated molecular signaling events occur in heart and skeletal muscle cells, and via metabolism and/or signaling, ketones may contribute to optimal skeletal muscle health and cardiac function. Of importance, when the use of ketones for ATP production and/or as signaling molecules becomes disturbed in the presence of underlying obesity, type 2 diabetes, and/or cardiovascular diseases, these changes may contribute to cardiometabolic disease. As a result of these disturbances in cardiometabolic disease, multiple approaches have been used to elevate circulating ketones with the goal of optimizing either ketone metabolism or ketone-mediated signaling. These approaches have produced significant improvements in heart and skeletal muscle during cardiometabolic disease with a wide range of benefits that include improved metabolism, weight loss, better glycemic control, improved cardiac and vascular function, as well as reduced inflammation and oxidative stress. Herein, we present the evidence that indicates that ketone therapy could be used as an approach to help treat cardiometabolic diseases by targeting cardiac and skeletal muscles.

A pilot study of alternative substrates in the critically Ill subject using a ketogenic feed

Bioenergetic failure caused by impaired utilisation of glucose and fatty acids contributes to organ dysfunction across multiple tissues in critical illness. Ketone bodies may form an alternative substrate source, but the feasibility and safety of inducing a ketogenic state in physiologically unstable patients is not known. Twenty-nine mechanically ventilated adults with multi-organ failure managed on intensive care units were randomised (Ketogenic n = 14, Control n = 15) into a two-centre pilot open-label trial of ketogenic versus standard enteral feeding. The primary endpoints were assessment of feasibility and safety, recruitment and retention rates and achievement of ketosis and glucose control. Ketogenic feeding was feasible, safe, well tolerated and resulted in ketosis in all patients in the intervention group, with a refusal rate of 4.1% and 82.8% retention. Patients who received ketogenic feeding had fewer hypoglycaemic events (0.0% vs. 1.6%), required less exogenous international units of insulin (0 (Interquartile range 0-16) vs.78 (Interquartile range 0-412) but had slightly more daily episodes of diarrhoea (53.5% vs. 42.9%) over the trial period. Ketogenic feeding was feasible and may be an intervention for addressing bioenergetic failure in critically ill patients. Clinical Trials.gov registration: NCT04101071.

New insights in the mechanisms of weight-loss maintenance: Summary from a Pennington symposium

Obesity is a chronic disease that affects more than 650 million adults worldwide. Obesity not only is a significant health concern on its own, but predisposes to cardiometabolic comorbidities, including coronary heart disease, dyslipidemia, hypertension, type 2 diabetes, and some cancers. Lifestyle interventions effectively promote weight loss of 5% to 10%, and pharmacological and surgical interventions even more, with some novel approved drugs inducing up to an average of 25% weight loss. Yet, maintaining weight loss over the long-term remains extremely challenging, and subsequent weight gain is typical. The mechanisms underlying weight regain remain to be fully elucidated. The purpose of this Pennington Biomedical Scientific Symposium was to review and highlight the complex interplay between the physiological, behavioral, and environmental systems controlling energy intake and expenditure. Each of these contributions were further discussed in the context of weight-loss maintenance, and systems-level viewpoints were highlighted to interpret gaps in current approaches. The invited speakers built upon the science of obesity and weight loss to collectively propose future research directions that will aid in revealing the complicated mechanisms involved in the weight-reduced state.

Tolerability and Acceptability of an Exogenous Ketone Monoester and Ketone Monoester/Salt Formulation in Humans

Exogenous ketone ester and ketone ester mixed with ketone free acid formulations are rapidly entering the commercial marketspace. Short-term animal and human studies using these products suggest significant potential for primary or secondary prevention of a number of chronic disease conditions. However, a number of questions need to be addressed by the field for optimal use in humans, including variable responses among available exogenous ketones at different dosages; frequency of dosing; and their tolerability, acceptability, and efficacy in long-term clinical trials. The purpose of the current investigation was to examine the tolerability, acceptability, and circulating R-beta-hydroxybutyrate (R-βHB) and glucose responses to a ketone monoester (KME) and ketone monoester/salt (KMES) combination at 5 g and 10 g total R-βHB compared with placebo control (PC). Fourteen healthy young adults (age: 21 ± 2 years, weight: 69.7 ± 14.2 kg, percent fat: 28.1 ± 9.3%) completed each of the five study conditions: placebo control (PC), 5 g KME (KME5), 10 g KME (KME10), 5 g (KMES5), and 10 g KMES (KMES10) in a randomized crossover fashion. Circulating concentrations of R-βHB were measured at baseline (time 0) following an 8-12 h overnight fast and again at 15, 30, 60, and 120 min following drink ingestion. Participants also reported acceptability and tolerability during each condition. Concentrations of R-βHB rose to 2.4 ± 0.1 mM for KME10 after 15 min, whereas KMES10 similarly peaked (2.1 ± 0.1 mM) but at 30 min. KME5 and KMES5 achieved similar peak R-βHB concentrations (1.2 ± 0.7 vs. 1.1 ± 0.5 mM) at 15 min. Circulating R-βHB concentrations were similar to baseline for each condition by 120 min. Negative correlations were observed between R-βHB and glucose at the 30 min time point for each condition except KME10 and PC. Tolerability was similar among KME and KMES, although decreases in appetite were more frequently reported for KMES. Acceptability was slightly higher for KMES due to the more frequently reported aftertaste for KME. The results of this pilot investigation illustrate that the KME and KMES products used increase circulating R-βHB concentrations to a similar extent and time course in a dose-dependent fashion with slight differences in tolerability and acceptability. Future studies are needed to examine variable doses, frequency, and timing of exogenous ketone administration for individuals seeking to consume ketone products for health- or sport performance-related purposes.

Effects of a two meals-a-day ketogenic diet on newly diagnosed obese patients with type 2 diabetes mellitus: A retrospective observational study

To investigate the effects of a two-meals-a-day energy-restricted ketogenic diet (KD) on newly diagnosed obese patients with type 2 diabetes mellitus. In total, 60 obese patients with newly diagnosed type 2 diabetes mellitus were divided into 2 groups: 1 group followed a 2-meals-a-day KD and the other group followed a conventional diabetic diet. Changes in weight, blood glucose, blood lipids, insulin resistance, and uric acid levels were observed before and after 2 months of adhering to the respective diets under energy restriction. Both groups showed significant reductions in weight, waist circumference, body mass index, total cholesterol, triglycerides, high-density lipoproteins, low-density lipoproteins, fasting blood glucose, fasting insulin, and glycated hemoglobin (P < .05). The twice-daily KD group showed more significant improvements in these parameters compared to the conventional diabetic diet group. In addition, the 2-meals-a-day KD group showed a slight increase in uric acid levels compared to the conventional diabetic diet control group (P < .05). The 2-meals-a-day KD can significantly improve weight, blood glucose, and lipid control in newly diagnosed obese patients with type 2 diabetes mellitus.

Implication of lipid turnover for the control of energy balance

The ongoing obesity epidemic is a consequence of a progressive energy imbalance. The energy-balance model (EBM) posits that obesity results from an excess in food intake and circulating fuels. A reversal in causality has been proposed recently in the form of the carbohydrate-insulin model (CIM), according to which fat storage drives energy imbalance. Under the CIM, dietary carbohydrates shift energy use in favour of storage in adipose tissue. The dynamics of lipid storage and mobilization could, therefore, be sensitive to changes in carbohydrate intake and represent a measurable component of the CIM. To characterize potential changes in lipid dynamics induced by carbohydrates, mathematical models were used. Here, we propose a coherent mathematical implementation of the CIM-energy deposition model (CIM-EDM), which includes lipid turnover dynamics. Using lipid turnover data previously obtained by radiocarbon dating, we build two cohorts of virtual patients and simulate lipid dynamics during ageing and weight loss. We identify clinically testable lipid dynamic parameters that discriminate between the CIM-EDM and an energy in, energy out implementation of the EBM (EBM-IOM). Using a clinically relevant two-month virtual trial, we additionally identify scenarios and propose mechanisms whereby individuals may respond differently to low-carbohydrate diets. This article is part of a discussion meeting issue 'Causes of obesity: theories, conjectures and evidence (Part II)'.

Discordance between gut-derived appetite hormones and energy intake in humans

Gut-derived hormones affect appetite and are thought to play an important role in body weight regulation. Dietary macronutrient composition can influence gut-derived appetite hormone concentrations, thereby providing theoretical basis for why some diets might facilitate weight loss better than others. We investigated postprandial gut-derived appetite hormones in 20 inpatient adults after 2 weeks of eating either a low carbohydrate (LC) or a low fat (LF) diet followed by the alternate diet in random order. A LC meal resulted in significantly greater postprandial GLP-1, GIP, and PYY but lower ghrelin compared to an isocaloric LF meal (all p≤0.02). However, differences in gut-derived appetite hormones were incommensurate with subsequent ad libitum energy intake over the rest of the day, which was 551±103 kcal (p<0.0001) greater with the LC as compared to the LF diet. The effects of gut-derived appetite hormones on ad libitum energy intake can be dominated by other diet-related factors, at least in the short-term.

Linking Migraine to Gut Dysbiosis and Chronic Non-Communicable Diseases

In the world, migraine is one of the most common causes of disability in adults. To date, there is no a single cause for this disorder, but rather a set of physio-pathogenic triggers in combination with a genetic predisposition. Among the factors related to migraine onset, a crucial role seems to be played by gut dysbiosis. In fact, it has been demonstrated how the intestine is able to modulate the central nervous system activities, through the gut-brain axis, and how gut dysbiosis can influence neurological pathologies, including migraine attacks. In this context, in addition to conventional pharmacological treatments for migraine, attention has been paid to an adjuvant therapeutic strategy based on different nutritional approaches and lifestyle changes able to positively modulate the gut microbiota composition. In fact, the restoration of the balance between the different gut bacterial species, the reconstruction of the gut barrier integrity, and the control of the release of gut-derived inflammatory neuropeptides, obtained through specific nutritional patterns and lifestyle changes, represent a possible beneficial additive therapy for many migraine subtypes. Herein, this review explores the bi-directional correlation between migraine and the main chronic non-communicable diseases, such as diabetes mellitus, arterial hypertension, obesity, cancer, and chronic kidney diseases, whose link is represented by gut dysbiosis.

Diet order affects energy balance in randomized crossover feeding studies that vary in macronutrients but not ultra-processing

BACKGROUND

Crossover studies can induce order effects, especially when they lack a wash-out period.

OBJECTIVE

To explore diet order effects on energy balance and food intake between randomized diet order groups in two inpatient crossover studies originally designed to compare within-subject differences in ad libitum energy intake between either minimally processed low carbohydrate (LC) versus low fat (LF) diets or macronutrient-matched diets composed of mostly minimally processed food (MPF) or ultra-processed food (UPF).

METHODS

Diet order group comparisons of changes in body weight, body composition, and differences in energy expenditure, and food intake were assessed over four weeks in 20 adults randomized to either the LC followed immediately by the LF diet (LC→LF) or the opposite order (LF→LC) as well as 20 adults randomized to either the MPF followed by UPF (MPF→UPF) diets or the opposite order (UPF→MPF).

RESULTS

Subjects randomized to LC→LF lost 2.9 ± 1.1 kg more body weight (p < 0.001) and 1.5 ± 0.6 kg more body fat (p = 0.03) than the LF→LC group likely because the LC→LF group consumed 922 ± 304 kcal/d less than the LF→LC group (p = 0.0024). Reduced energy intake in LC→LF vs LF→LC was driven by the last two weeks (-1610 ± 306 kcal/d; p<0.00001) perhaps due to carryover effects of gut adaptations over the first two weeks arising from large differences in the mass of food (1295 ± 209 g/d; p<0.00001) and fiber intake (58 ± 5 g/d; p<0.00001). There were no diet order effects on ad libitum energy intake, body weight, or body composition change between UPF→MPF versus MPF→UPF groups.

CONCLUSIONS

Diet order influences daily ad libitum energy intake, body weight change, and fat change within the context of a 4-week crossover inpatient diet study varying in macronutrients, but not varying in extent and purpose of processing.

Funding sources

Intramural Research Program of the National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health.

Clinical Trial Registration

NCT03407053 and NCT03878108.

Effects of ketone bodies on energy expenditure, substrate utilization, and energy intake in humans

The potential of ketogenic approaches to regulate energy balance has recently gained attention since ketones may influence both energy expenditure and energy intake. In this narrative review, we summarized the most relevant evidence about the role of ketosis on energy expenditure, substrate utilization, and energy intake in humans. We considered different strategies to induce ketosis, such as fasting, dietary manipulation, and exogenous ketone sources. In general, ketosis does not have a major influence on energy expenditure but promotes a shift in substrate utilization towards ketone body oxidation. The strategies to induce ketosis by reduction of dietary carbohydrate availability (e.g., ketogenic diets) do not independently influence energy intake, being thus equally effective for weight loss as diets with higher carbohydrate content. In contrast, the intake of medium-chain triglycerides and ketone esters induces ketosis and appears to increase energy expenditure and reduce energy intake in the context of high carbohydrate availability. These latter strategies lead to slightly enhanced weight loss. Unfortunately, distinguishing the effects of the various ketogenic strategies per se from the effects of other physiological responses is not possible with the available human data. Highly controlled, inpatient studies using targeted strategies to isolate the independent effects of ketones are required to adequately address this knowledge gap.

A phenotypic approach to obesity treatment

Obesity is a chronic disease that increases morbidity and mortality and adversely affects quality of life. The rapid rise of obesity has outpaced the development and deployment of effective therapeutic interventions, thereby creating a global health crisis. The presentation, complications, and response to obesity treatments vary, yet lifestyle modification, which is the foundational therapeutic intervention for obesity, is often "one size fits all." The concept of personalized medicine uses genetic and phenotypic information as a guide for disease prevention, diagnosis, and treatment and has been successfully applied in diseases such as cancer, but not in obesity. As we gain insight into the pathophysiologic mechanisms of obesity and its phenotypic expression, specific pathways can be targeted to yield a greater, more sustained therapeutic impact in an individual patient with obesity. A phenotype-based pharmacologic treatment approach utilizing objective measures to classify patients into predominant obesity mechanism groups resulted in greater weight loss (compared with a non-phenotype-based approach) in a recent study by Acosta and colleagues. In this review, we discuss the application of lifestyle modifications, behavior therapy and pharmacotherapy using the obesity phenotype-based approach as a framework.

The ketogenic diet promotes triacylglycerol recycling in white adipose tissue and uncoupled fat oxidation in brown adipose tissue, but does not reduce adiposity in rats

The purpose of this study was to determine whether the weight-reducing and fat burning effects of the ketogenic diet (KD) could be attributed to alterations in the energy dissipating pathways of brown adipose tissue (BAT) uncoupled oxidation, and white adipose tissue (WAT) browning and triacylglycerol (TAG) recycling. To investigate this, male Wistar rats were fed one of the following three diets for either 8 or 16 weeks: a standard chow (SC), a high-fat, sucrose-enriched (HFS) obesogenic diet, or a KD. At the end of the intervention, subcutaneous inguinal (Sc Ing) and epididymal (Epid) fat, and interscapular and aortic BAT (iBAT and aBAT, respectively) were extracted. These tissues were used for the analysis of proteins involved in WAT browning and thermogenesis. Isolated adipocytes from WAT were assayed for basal and isoproterenol (Iso)-stimulated lipolysis and basal and insulin-stimulated lipogenesis, and BAT adipocytes were assayed for the determination of coupled and uncoupled glucose and palmitate oxidation. Adiposity similarly increased in HFS- and KD-fed rats at weeks 8 and 16. However, in HFS-fed animals insulin-stimulated lipogenesis and Iso-stimulated lipolysis were impaired in WAT adipocytes, whereas in KD-fed animals these pathways remained intact. The KD also significantly elevated WAT glycerol kinase levels, and favored TAG recycling under conditions of enhanced lipolysis. In BAT, the KD significantly increased uncoupling protein-1 levels and uncoupled fat oxidation. In summary, the KD preserved insulin sensitivity and lipolytic capacity in WAT and also upregulated energy-dissipating pathways in BAT, but it was not sufficient to prevent an increase in adiposity.

Adherence to ketogenic diet in lifestyle interventions in adults with overweight or obesity and type 2 diabetes: a scoping review

BACKGROUND/OBJECTIVES

Despite the evidence supporting the efficacy of the ketogenic diet (KD) on weight and type 2 diabetes (T2D) management, adherence to the KD is challenging. Additionally, no studies have reported changes in PA among individuals with overweight/obesity and T2D who have followed KD. We mapped out the methods used to assess adherence to the KD and level of physical activity (PA) in lifestyle interventions for weight and T2D management in individuals with overweight/obesity and T2D and compared levels of KD adherence and PA in these interventions.

METHODS

Articles published between January 2005 and March 2022 were searched in MEDLINE, CINAHL, and Scopus. Studies that included KD in lifestyle interventions for adults with T2D and overweight/obesity and measured ketone levels were included.

RESULTS

The eleven included studies comprised eight randomized controlled trials. They mainly used self-reported measures to evaluate adherence to the KD and level of PA. We found studies reported higher carbohydrate intake and lower fat intake than the KD regimen. Great inconsistencies were found among studies on the measurement and reporting of ketone and PA levels.

CONCLUSION

Our results demonstrated the need to develop intervention strategies to improve adherence to the KD, as well as the necessity of developing standardized diet and PA assessment tools to establish a stronger evidence base for including KD in lifestyle interventions for weight and T2D management among adults with overweight/obesity and T2D.

Dietary interventions improve diabetic kidney disease, but not peripheral neuropathy, in a db/db mouse model of type 2 diabetes

Patients with type 2 diabetes often develop the microvascular complications of diabetic kidney disease (DKD) and diabetic peripheral neuropathy (DPN), which decrease quality of life and increase mortality. Unfortunately, treatment options for DKD and DPN are limited. Lifestyle interventions, such as changes to diet, have been proposed as non-pharmacological treatment options for preventing or improving DKD and DPN. However, there are no reported studies simultaneously evaluating the therapeutic efficacy of varying dietary interventions in a type 2 diabetes mouse model of both DKD and DPN. Therefore, we compared the efficacy of a 12-week regimen of three dietary interventions, low carbohydrate, caloric restriction, and alternate day fasting, for preventing complications in a db/db type 2 diabetes mouse model by performing metabolic, DKD, and DPN phenotyping. All three dietary interventions promoted weight loss, ameliorated glycemic status, and improved DKD, but did not impact percent fat mass and DPN. Multiple regression analysis identified a negative correlation between fat mass and motor nerve conduction velocity. Collectively, our data indicate that these three dietary interventions improved weight and glycemic status and alleviated DKD but not DPN. Moreover, diets that decrease fat mass may be a promising non-pharmacological approach to improve DPN in type 2 diabetes given the negative correlation between fat mass and motor nerve conduction velocity.

The Effects of Ketogenic Diet on Insulin Sensitivity and Weight Loss, Which Came First: The Chicken or the Egg?

The ketogenic diet (KD) is, nowadays, considered an interesting nutritional approach for weight loss and improvement in insulin resistance. Nevertheless, most of the studies available in the literature do not allow a clear distinction between its effects on insulin sensitivity per se, and the effects of weight loss induced by KDs on insulin sensitivity. In this review, we discuss the scientific evidence on the direct and weight loss mediated effects of KDs on glycemic status in humans, describing the KD's biochemical background and the underlying mechanisms.

CDK6: an attractive therapeutic target for T-ALL/LBL

INTRODUCTION

Human T-cell acute lymphoblastic leukemia/T-cell lymphoblastic lymphoma (T-ALL/LBL) is a type of cancer that originates from the bone marrow and spreads quickly to other organs. Long-term survival rate with current available chemotherapy is less than 20%. Despite the potentially huge market, a truly effective and safe therapy for T-ALL/LBL is elusive. Thus, it is imperative to identify new therapeutic ways to target essential pathways in T-ALL that regulate the proliferation and survival of these cancer cells.

AREAS COVERED

The role of the Cyclin-dependent kinase 6 (CDK6) pathway in human T-ALL is of significant interest with major clinical/translational relevance. This review covers the recent advances in elucidating the essential roles of CDK6 and its closely regulated networks in proliferation, survival, and metabolism of T-ALL cells, with new insight into its mechanisms of action which hopefully could trigger the identification of new therapeutic avenues.

EXPERT OPINION

Animal models showed that inhibition of CDK6 and its related networks blocked initiation, growth, and survival of T-ALL in vivo. Numerous clinical trials of CDK4/6 inhibitors are ongoing in T-ALL. Specific CDK6 inhibitors alone or novel combination regimens may hopefully delay the progression, or even reverse the symptoms of T-ALL, leading to disease eradication and cure.

Association between ß-Hydroxybutyrate Plasma Concentrations after Hypocaloric Ketogenic Diets and Changes in Body Composition

BACKGROUND

Early studies show that ketogenic diets (KDs) lead to preferential loss of fat mass (FM), whereas preserving fat-free mass (FFM). Additionally, animal data support the anticatabolic effects of DL-3-hydroxybutyrate. From our knowledge, a potential association between ß-hydroxybutyrate (ßHB) plasma concentrations and changes in body composition has never been explored.

OBJECTIVES

The main aim of this analysis was to determine if ßHB plasma concentrations, following hypocaloric KDs, were associated with FM and FFM changes in men and women with obesity.

METHODS

Data from 199 individuals (BMI = 36.6 ± 4.3 kg/m2; age = 43.6 ± 9.8 y; 82 men) were collated from 3 weight loss studies employing common measures of body composition (air displacement plethysmography) and ßHB plasma concentration (ELISA). The association between ßHB and weight, FM and FFM loss (kg), and %FFM loss (%FFML) was investigated with Spearman correlation. Multivariable linear regression was used to determine if ßHB was a significant predictor of the changes in anthropometric variables, after adjusting for confounding factors.

RESULTS

ßHB was not associated with FFML (% or kg), but a weak positive association was seen with FM loss (r = 0.182, P = 0.01, n = 199) and a trend with weight loss (r = 0.128, P = 0.072, n = 199). ßHB was a significant predictor of both weight and FM loss (kg), after adjusting for age, sex, baseline BMI, and intervention study.

CONCLUSIONS

The magnitude of ketosis is not associated with FFM preservation. However, the higher the level of ketosis, the greater the weight and FM loss. Further studies are needed to confirm these findings and to explore the mechanisms involved. This trial was registered at clinicaltrials.gov identifier as NCT01834859, NCT04051190, NCT02944253.

High-intensity interval training prevents muscle mass loss in overweight Chilean young adults during a hypocaloric-Mediterranean diet: a randomized trial

The hypocaloric Mediterranean diet (MD) mainly reduces fat mass but inevitably causes a loss of skeletal muscle mass. High-intensity interval training (HIIT) seems to have advantages in preserving muscle mass during a hypocaloric regime. Our study compares body composition and metabolic changes in overweight and obese Chilean women and men after 3 months of weight loss treatment with a Mediterranean-type hypocaloric diet, HIIT, or a combination of both. The study included 83 overweight or obese women and men between the ages of 25 and 50. The subjects were randomly assigned to one of the three intervention groups: (1) MD, (2) EX, and (3) MD + EX. Baseline and post-intervention measurements included: (a) body composition by dual-beam densitometry, muscle, and fat measurements by thigh ultrasound and computed tomography; (b) handgrip and quadriceps muscle strength; (c) exercise performance by peak oxygen consumption, peak load, work efficiency, and exercise energy expenditure; and (d) metabolic parameters. Out of 83 participants, the retention rate was 49% due to low compliance with the interventions. As expected, the MD group resulted in significantly greater weight loss (MD -7%, EX -0.6% and MD + EX -5.3%) and appendicular fat mass loss (MD -11.1%, EX -2.9, MD + EX -10.2%) but was associated with significant lean tissue loss (2.8%), which was prevented by HIIT (EX -0.1 and MD + EX -0.6%). Metabolic and glycoxidative parameters remained unchanged, irrespective of changes in body composition. Hypocaloric diets remain the most effective means to lose weight and body fat. However, it induces a loss of lean body mass when not accompanied by exercise training. This study shows that HIIT prevents the loss of muscle mass caused by a hypocaloric Mediterranean diet.

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.

Impact of one-day fasting, ketogenic diet or exogenous ketones on control of energy balance in healthy participants

BACKGROUND & AIMS

Oral ketone supplements may mimic the beneficial effects of endogenous ketones on energy metabolism as β-hydroxybutyrate has been proposed to increase energy expenditure and improve body weight regulation. Therefore, our objective was to compare the effects of a one-day isocaloric ketogenic diet, fasting and supplementation with ketone salts on energy expenditure and appetite perception.

METHODS

Eight healthy young adults (4 women, 4 men, age 24 ± 3 years, BMI 24.3 ± 3.1 kg/m²) participated in a randomized cross-over trial with four 24 h-interventions in a whole room indirect calorimeter at a physical activity level of 1.65: (i) total fasting (FAST), (ii) isocaloric ketogenic diet (3.1% energy from carbohydrates (CHO), KETO), (iii) isocaloric control diet (47.4% energy from CHO, ISO), and (iv) ISO supplemented with 38.7 g/d ketone salts (exogenous ketones, EXO). Effects on serum ketone levels (15 h-iAUC), energy metabolism (total energy expenditure, TEE; sleeping energy expenditure, SEE; macronutrient oxidation) and subjective appetite were measured.

RESULTS

Compared to ISO, ketone levels were considerably higher with FAST and KETO and little higher with EXO (all p > 0.05). Total and sleeping energy expenditure did not differ between ISO, FAST and EXO whereas KETO increased TEE (+110 ± 54 kcal/d vs. ISO, p < 0.05) and SEE (+201 ± 90 kcal/d vs. ISO, p < 0.05). CHO oxidation was slightly decreased with EXO compared to ISO (-48 ± 27 g/d, p < 0.05) resulting in a positive CHO balance (p < 0.05). No differences between the interventions were found for subjective appetite ratings (all p > 0.05).

CONCLUSION

A 24 h-ketogenic diet may contribute to maintain a neutral energy balance by increasing energy expenditure. Exogenous ketones in addition to an isocaloric diet did not improve regulation of energy balance.

CLINICAL TRIAL REGISTRATION

NCT04490226 https://clinicaltrials.gov/.

Body Fat Distribution, Fasting Insulin Levels, and Insulin Secretion: A Bidirectional Mendelian Randomization Study

CONTEXT

Hyperinsulinemia and adiposity are associated with one another, but the directionality of this relation is debated.

OBJECTIVE

Here, we tested the direction of the causal effects of fasting insulin (FI) levels and body fat accumulation/distribution using 2-sample bidirectional Mendelian randomization (MR).

METHODS

We included summary statistics from large-scale genome-wide association studies for body mass index (BMI, n = 806 834), waist to hip ratio adjusted for BMI (WHRadjBMI, n = 694 649), abdominal subcutaneous, visceral and gluteofemoral adipose tissue (n = 38 965), FI levels (n = 98 210), pancreatic islets gene expression (n = 420), and hypothalamus gene expression (n = 155). We used inverse variance-weighted and robust MR methods that relied on statistically and biologically driven genetic instruments.

RESULTS

Both BMI and WHRadjBMI were positively associated with FI. Results were consistent across all robust MR methods and when variants mapped to the hypothalamus (presumably associated with food behavior) were included. In multivariable MR analyses, when waist circumference and BMI were mutually adjusted, the direct effect of waist circumference on FI was 2.43 times larger than the effect of BMI on FI. FI was not associated with adiposity. By contrast, using genetic instruments mapped to gene expression in pancreatic islets (presumably more specific to insulin secretion), insulin was positively associated with BMI and abdominal subcutaneous and gluteofemoral adipose tissue, but not with visceral adipose tissue.

CONCLUSION

Although these results will need to be supported by experimental investigations, results of this MR study suggest that abdominal adiposity may be a key determinant of circulating insulin levels. Alternatively, insulin secretion may promote peripheral adipose tissue accumulation.

Impact of Body Composition on Sleep and Its Relationship with Sleep Disorders: Current Insights

Sleep is involved in many physiological processes and is essential for both physical and mental health. Obesity and sleep deprivation due to sleep disorders are major public health issues. Their incidence is increasing, and they have a wide range of adverse health-related consequences, including life-threatening cardiovascular disease. The impact of sleep on obesity and body composition is well-known, and many studies have shown an association between insufficient or excessive sleep duration and obesity, body fat percentage, and weight gain. However, there is growing evidence of the effects of body composition on sleep and sleep disorders (particularly sleep disordered breathing) through anatomical and physiological mechanisms (nocturnal fluid shift, core body temperature, or diet). Although some research has been conducted on the bidirectional effects of sleep-disordered breathing and body composition, the specific effects of obesity and body composition on sleep and the underlying mechanisms that explain these effects remain unclear. Therefore, this review summarizes the findings on the effects of body composition on sleep and draws conclusions and proposals for future research in this field.

Obesity-related parameters in carriers of some BDNF genetic variants may depend on daily dietary macronutrients intake

Some common single-nucleotide polymorphisms of the brain-derived neurotrophic factor (BDNF) gene have been associated not only with the neurodegenerative diseases but also with some eating disorders. The aim of this study was to assess the possible differences in the obesity-related and glucose metabolism parameters between some BDNF genotypes', that may depend on the daily energy and macronutrients intake. In 484 adult participants we performed the anthropometric measurements, body composition analysis, and body fat distribution. The daily dietary intake was assessed using the 3-day food intake diaries. Blood glucose and insulin concentrations were measured at fasting and during oral glucose tolerance tests. Moreover, the visceral adipose tissue/subcutaneous adipose tissue (VAT/SAT) ratio and homeostatic model assessment of insulin resistance were calculated. We noted that participants carrying the GG genotype had lower skeletal muscle mass and fat free mass (FFM) when carbohydrate intake was > 48%, whereas they presented higher fat-free mass (FFM), and surprisingly higher total cholesterol and LDL-C concentrations when daily fiber intake was > 18 g. Moreover, in these subjects we noted higher waist circumference, BMI, and fasting glucose and insulin concentrations, when > 18% of total daily energy intake was delivered from proteins, and higher VAT content and HDL-C concentrations when > 30% of energy intake was derived from dietary fat. Our results suggest that glucose homeostasis and obesity-related parameters in carriers of some common variants of BDNF gene, especially in the GG (rs10835211) genotype carriers, may differ dependently on daily energy, dietary macronutrients and fiber intake.

Dietary ketone ester attenuates the accretion of adiposity and liver steatosis in mice fed a high-fat, high-sugar diet

Objective: The ketone diester, R,S-1,3-butanediol diacetoacetate (BD-AcAc2), attenuates the accretion of adiposity and reduces hepatic steatosis in high-fat diet-induced obese mice when carbohydrate energy is removed from the diet to accommodate energy from the ester. Reducing carbohydrate energy is a potential confounder due to the well-known effects of carbohydrate restriction on components of energy balance and metabolism. Therefore, the current investigation was designed to determine whether the addition of BD-AcAc2 to a high-fat, high-sugar diet (with no reduction in carbohydrate energy) would attenuate the accretion of adiposity and markers of hepatic steatosis and inflammation. Methods: Sixteen 11-week-old male C57BL/6J mice were randomized to one of two groups for 9 weeks (n = 8 per group): 1) Control (CON, HFHS diet) or 2) Ketone ester (KE, HFHS diet + BD-AcAc2, 25% by kcals). Results: Body weight increased by 56% in CON (27.8 ± 2.5 to 43.4 ± 3.7 g, p < 0.001) and by 13% in KE (28.0 ± 0.8 to 31.7 ± 3.1 g, p = 0.001). Non-alcoholic fatty liver disease activity scores (NAS) for hepatic steatosis, inflammation, and ballooning were lower in the KE group compared to CON (p < 0.001 for all). Markers of hepatic inflammation [Tnfα (p = 0.036); Mcp1 (p < 0.001)], macrophage content [(Cd68 (p = 0.012)], and collagen deposition and hepatic stellate cell activation [(αSma (p = 0.004); Col1A1 (p < 0.001)] were significantly lower in the KE group compared to CON. Conclusion: These findings extend those of our previous work and show that BD-AcAc2 attenuates the accretion of adiposity and reduces markers of liver steatosis, inflammation, ballooning, and fibrosis in lean mice placed on a HFHS diet where carbohydrate energy was not removed to accommodate energy from addition of the diester.

Mediterranean diet in the management and prevention of obesity

The current pandemic of obesity represents a major global public health problem, mainly due to its association with chronic non-communicable disabling conditions and with increased mortality. Population aging increases the chances of non-communicable chronic diseases allowing a longer exposure to risk factors for these disabling conditions. Obesity is a major risk factor contributing to pathological aging. Numerous epidemiological studies have shown that the risk of death due to cardiovascular disease and cancer increases progressively as overweight and obesity rise. Nutrition research is now focused on the effects of combinations of foods in dietary patterns instead of those of single nutrients or foods. The dietary model with the largest body of evidence of health benefit is that traditionally followed by inhabitants of some Mediterranean countries. There is evidence confirming the inverse association of adhering to Mediterranean diet with overweight and obesity. Four meta-analyses of randomized controlled trials, including up to 16 trials, have shown a greater reduction of body weight and BMI with MedDiet compared to other diets, while a meta-analysis of 7 prospective cohort studies, found a reduced risk of becoming obese and gaining weight over time associated with a higher adherence to MedDiet. This narrative review examines studies reporting inverse associations of a higher adherence to the MedDiet with overweight/obesity and with age-associated chronic diseases related to obesity.

Low carbohydrate high fat ketogenic diets on the exercise crossover point and glucose homeostasis

In exercise science, the crossover effect denotes that fat oxidation is the primary fuel at rest and during low-intensity exercise with a shift towards an increased reliance on carbohydrate oxidation at moderate to high exercise intensities. This model makes four predictions: First, >50% of energy comes from carbohydrate oxidation at ≥60% of maximum oxygen consumption (VO2max), termed the crossover point. Second, each individual has a maximum fat oxidation capacity (FATMAX) at an exercise intensity lower than the crossover point. FATMAX values are typically 0.3-0.6 g/min. Third, fat oxidation is minimized during exercise ≥85%VO2max, making carbohydrates the predominant energetic substrate during high-intensity exercise, especially at >85%VO2max. Fourth, high-carbohydrate low-fat (HCLF) diets will produce superior exercise performances via maximizing pre-exercise storage of this predominant exercise substrate. In a series of recent publications evaluating the metabolic and performance effects of low-carbohydrate high-fat (LCHF/ketogenic) diet adaptations during exercise of different intensities, we provide findings that challenge this model and these four predictions. First, we show that adaptation to the LCHF diet shifts the crossover point to a higher %VO2max (>80%VO2max) than previously reported. Second, substantially higher FATMAX values (>1.5 g/min) can be measured in athletes adapted to the LCHF diet. Third, endurance athletes exercising at >85%VO2max, whilst performing 6 × 800 m running intervals, measured the highest rates of fat oxidation yet reported in humans. Peak fat oxidation rates measured at 86.4 ± 6.2%VO2max were 1.58 ± 0.33 g/min with 30% of subjects achieving >1.85 g/min. These studies challenge the prevailing doctrine that carbohydrates are the predominant oxidized fuel during high-intensity exercise. We recently found that 30% of middle-aged competitive athletes presented with pre-diabetic glycemic values while on an HCLF diet, which was reversed on LCHF. We speculate that these rapid changes between diet, insulin, glucose homeostasis, and fat oxidation might be linked by diet-induced changes in mitochondrial function and insulin action. Together, we demonstrate evidence that challenges the current crossover concept and demonstrate evidence that a LCHF diet may also reverse features of pre-diabetes and future metabolic disease risk, demonstrating the impact of dietary choice has extended beyond physical performance even in athletic populations.