Carbohydrate-restricted diets high in either monounsaturated fat or protein are equally effective at promoting fat loss and improving blood lipids

Differences in weight loss outcomes for males and females on a low-carbohydrate diet: A systematic review

It has been widely demonstrated that there are a broad range of individual responses to all weight management regimens, often masked by reports of the mean. Identifying features of responders and non-responders to weight loss regimens enables a more tailored approach to the provision of weight management advice. Low-carbohydrate diets are currently popular, and anecdote suggests that males are more successful at losing weight using this approach. This is feasible given the physiological and socio-psychological differences between the genders. We analysed the extent and variation in weight change for males and females separately through a systematic search for all low-carbohydrate diet trials published since 1985. Very few studies compared weight loss outcomes by gender and, of those that did, most lacked supporting data. The majority of studies reported no gender difference but when a gender difference was found, males were more frequently reported as losing more weight than females on a low-carbohydrate diet. The lack of gender stratification in weight loss trials is concerning, as there are a range of gender-based factors that affect weight loss outcomes. This study highlights the importance of examining weight change for males and females separately, since as failure to do so may mask any potential differences, which, if detected, could assist with better weight loss outcomes.

Acute supplementation with whey protein or collagen does not alter appetite in healthy women: a randomised double-blind and crossover pilot study

Protein quality has an important role in increasing satiety. Evidence suggests that whey protein (WP) provides satiety via gastrointestinal hormone secretion. Hydrolysed collagen supplementation can also stimulate the production of incretins and influence satiety and food intake. Thus, we sought to compare the effect of acute supplementation of WP or hydrolysed collagen on post-intervention appetite and energy consumption. This was a randomised, double-blind, crossover pilot study with ten healthy adult women (22·4 years/old) who were submitted to acute intake (single dose) of a beverage containing WP (40 g of concentrated WP) or hydrolysed collagen (40 g). Subjective appetite ratings (feelings of hunger, desire to eat and full stomach) were measured using the Visual Analog Scale (VAS), energy intake was quantified by ad libitum cheese bread consumption 2 hours after supplementation and blood was collected for leptin and glucose determination. There was no difference between treatment groups in the perception of hunger (P = 0·983), desire to eat (P = 0·326), full stomach feeling (P = 0·567) or food consumption (P = 0·168). Leptin concentrations at 60 min post supplementation were higher when subjects received hydrolysed collagen (P = 0·006). Acute supplementation with hydrolysed collagen increased leptin levels in comparison with WP, but had no effect on appetite measured by feelings of hunger, desire to eat, full stomach feeling (VAS) or energy consumption.

Probiotic Strains Isolated from an Olympic Woman’s Weightlifting Gold Medalist Increase Weight Loss and Exercise Performance in a Mouse Model

Obesity is a worldwide health problem. Calorie-restricted diets constitute a common intervention for treating obesity. However, an improper calorie-restricted diet can lead to malnutrition, fatigue, poor concretion, muscle loss, and reduced exercise performance. Probiotics have been introduced as an alternative treatment for obesity. In the present study, we tested the weight loss and exercise performance enhancement effectiveness of probiotic strains of different origins, including four isolated from an Olympic weightlifting gold medalist (Bifidobacterium longum subsp. longum OLP-01, Lactobacillus plantarum PL-02, Lactobacillus salivarius subsp. salicinius SA-03, and Lactococcus lactis subsp. lactis LY-66). A high-fat diet (HFD) was used to induce obesity in 16 groups of mice (n = 8/group). The mice were administered probiotic supplements at a dosage of 4.1 × 10⁹ CFU/kg/day for 10 weeks. All probiotic supplementation groups showed a significant reduction in body weight and fat mass compared with the HFD group. TYCA06, CS-773, BLI-02, PL-02, bv-77, and OLP-01 were the most effective in facilitating weight loss and fat reduction, which may be due to fatty-acid absorbing activity. PL-02, LY-66, TYCA06, CS-773, and OLP-01 elevated the animals’ grip strength and exhaustive running duration. PL-02, LY-66, and OLP-01 increased tissue glycogen (liver and muscle) levels and muscle capillary density and reduced blood lactate production levels after exercise. In conclusion, OLP-01, PL-02, LY-66, TYCA06, and CS-773 were highly effective in enhancing weight loss and exercise performance. This study should be repeated on humans in the future to further confirm the findings.

Does the weight loss efficacy of alternate day fasting differ according to sex and menopausal status?

BACKGROUND AND AIMS

This study examined if the weight loss and metabolic benefits of alternate day fasting (ADF) varies according to sex and menopausal status in adults with obesity.

METHODS AND RESULTS

This secondary analysis pooled the data of men and women (n = 75) who participated in three 12-week ADF studies (500 kcal fast day; alternated with an ad libitum intake feast day). Body weight decreased in premenopausal women (-4.6 ± 3.2%), postmenopausal women (-6.5 ± 3.2%) and men (-6.2 ± 4.4%) (main effect of time, P < 0.001), with no difference between groups (no group × time interaction). Energy intake on fast days was higher than prescribed in all groups (∼400-500 excess kcal consumed), with no differences between groups. Fat mass, lean mass, fasting insulin, and insulin resistance, and blood pressure decreased similarly in all groups (main effect of time, P < 0.05 for all comparisons). LDL cholesterol decreased more in postmenopausal versus premenopausal women (group × time interaction, P = 0.01). Fasting glucose, HDL cholesterol, and triglycerides remained unchanged in all groups.

CONCLUSION

These findings suggest that the weight loss and metabolic benefits of ADF do not generally vary according to sex or menopausal status in adults with obesity.

TRIAL REGISTRATION

Clinicaltrials.gov, NCT00960505; NCT03528317.

Effects of high protein, low-glycemic index diet on lean body mass, strength, and physical performance in late postmenopausal women: a randomized controlled trial

OBJECTIVE

To investigate whether increasing protein consumption to twice the recommended daily allowance (RDA) by The Institute of Medicine affects lean body mass (LBM), muscle strength, and physical performance in late postmenopausal women.

METHODS

Parallel-group randomized trial with 26 apparently healthy women aged ≥ 65 years. Participants were randomly assigned to low-glycemic index diets with protein consumption at current RDA (0.8 g/kg body weight) or twice the RDA (2RDA, 1.6 g/kg body weight). Protein intake was assessed by 24-hours urinary nitrogen excretion. Change in LBM was measured by dual-energy X-ray absorptiometry at 3 and 6 months. Secondary outcomes were appendicular lean mass, handgrip strength by dynamometry, and physical performance by gait speed.

RESULTS

Mean age was 70.8 ± 3.6 years, and mean BMI was 26.1 ± 3.5 kg/m2 in the overall sample. The RDA and 2RDA groups did not differ regarding baseline dietary intake. Changes from baseline in LBM (0.07 kg; 95% CI, -0.39; 0.52 kg; P = 0.100) and appendicular lean mass (0.07 kg; 95% CI, -0.34; 0.47 kg; P = 0.100) did not differ between the groups. Total body fat (-1.41 kg; 95% CI, -2.62; 0.20 kg; P = 0.019) and trunk fat mass (-0.90 kg; 95% CI, -1.55; -0.24 kg; P = 0.005) decreased similarly in both groups at the end of intervention. Adjusting for baseline BMI did not alter these findings. Handgrip strength and 4-m gait speed increased after the intervention, with no significant difference between the groups.

CONCLUSIONS

Protein intake exceeding the RDA did not increase LBM, strength, and physical performance in a sample of late postmenopausal woman consuming a low-glycemic index diet for 6 months.

Examining differences between overweight women and men in 12-month weight loss study comparing healthy low-carbohydrate vs. low-fat diets

Background/objectives

Biological sex factors and sociocultural gender norms affect the physiology and behavior of weight loss. However, most diet intervention studies do not report outcomes by sex, thereby impeding reproducibility. The objectives of this study were to compare 12-month changes in body weight and composition in groups defined by diet and sex, and adherence to a healthy low carbohydrate (HLC) vs. healthy low fat (HLF) diet.

Participants/methods

This was a secondary analysis of the DIETFITS trial, in which 609 overweight/obese nondiabetic participants (age, 18–50 years) were randomized to a 12-month HLC (n = 304) or HLF (n = 305) diet. Our first aim concerned comparisons in 12-month changes in weight, fat mass, and lean mass by group with appropriate adjustment for potential confounders. The second aim was to assess whether or not adherence differed by diet-sex group (HLC women n = 179, HLC men n = 125, HLF women n = 167, HLF men n = 138).

Results

12-month changes in weight (p < 0.001) were different by group. HLC produced significantly greater weight loss, as well as greater loss of both fat mass and lean mass, than HLF among men [−2.98 kg (−4.47, −1.50); P < 0.001], but not among women. Men were more adherent to HLC than women (p = 0.02). Weight loss estimates within group remained similar after adjusting for adherence, suggesting adherence was not a mediator.

Conclusions

By reporting outcomes by sex significant weight loss differences were identified between HLC and HLF, which were not recognized in the original primary analysis. These findings highlight the need to consider sex in the design, analysis, and reporting of diet trials.

Protein Intake at Twice the RDA in Older Men Increases Circulatory Concentrations of the Microbiome Metabolite Trimethylamine-N-Oxide (TMAO)

Higher dietary protein intake is increasingly recommended for the elderly; however, high protein diets have also been linked to increased cardiovascular disease (CVD) risk. Trimethylamine-N-oxide (TMAO) is a bacterial metabolite derived from choline and carnitine abundant from animal protein-rich foods. TMAO may be a novel biomarker for heightened CVD risk. The purpose of this study was to assess the impact of a high protein diet on TMAO. Healthy men (74.2 ± 3.6 years, n = 29) were randomised to consume the recommended dietary allowance of protein (RDA: 0.8 g protein/kg bodyweight/day) or twice the RDA (2RDA) as part of a supplied diet for 10 weeks. Fasting blood samples were collected pre- and post-intervention for measurement of TMAO, blood lipids, glucose tolerance, insulin sensitivity, and inflammatory biomarkers. An oral glucose tolerance test was also performed. In comparison with RDA, the 2RDA diet increased circulatory TMAO (p = 0.002) but unexpectedly decreased renal excretion of TMAO (p = 0.003). LDL cholesterol was increased in 2RDA compared to RDA (p = 0.049), but no differences in other biomarkers of CVD risk and insulin sensitivity were evident between groups. In conclusion, circulatory TMAO is responsive to changes in dietary protein intake in older healthy males.

Changes in Kidney Function Do Not Differ between Healthy Adults Consuming Higher- Compared with Lower- or Normal-Protein Diets: A Systematic Review and Meta-Analysis

Background

Higher-protein (HP) diets are advocated for several reasons, including mitigation of sarcopenia, but their effects on kidney function are unclear.

Objective

This meta-analysis was conducted to determine the effect of HP intakes on kidney function in healthy adults.

Methods

We conducted a systematic review and meta-analysis of trials comparing HP (≥1.5 g/kg body weight or ≥20% energy intake or ≥100 g protein/d) with normal- or lower-protein (NLP; ≥5% less energy intake from protein/d compared with HP group) intakes on kidney function. Medline and EMBASE databases were searched. Randomized controlled trials comparing the effects of HP with NLP (>4 d duration) intakes on glomerular filtration rate (GFR) in adults without kidney disease were included.

Results

A total of 2144 abstracts were reviewed, with 40 articles selected for full-text review; 28 of these were analyzed and included data from 1358 participants. Data were analyzed using random-effects meta-analysis (RevMan 5; The Cochrane Collaboration), meta-regression (STATA; StataCorp), and dose-response analysis (Prism; GraphPad). Analyses were conducted using postintervention (post) GFR and the change in GFR from preintervention to post. The post-only comparison showed a trivial effect for GFR to be higher after HP intakes [standardized mean difference (SMD): 0.19; 95% CI: 0.07, 0.31; P = 0.002]. The change in GFR did not differ between interventions (SMD: 0.11; 95% CI: -0.05, 0.27; P = 0.16). There was a linear relation between protein intake and GFR in the post-only comparison (r = 0.332, P = 0.03), but not between protein intake and the change in GFR (r = 0.184, P = 0.33). The main limitation of the current analysis is the unclear risk of selection bias of the included trials.

Conclusions

Postintervention GFR comparisons indicate that HP diets result in higher GFRs; however, when changes in GFR were compared, dietary protein had no effect. Our analysis indicates that HP intakes do not adversely influence kidney function on GFR in healthy adults.

The effect of meals on bone turnover - a systematic review with focus on diabetic bone disease

INTRODUCTION

Type 2 diabetes is associated with an increased risk of bone fractures. Bone mineral density (BMD) is increased and bone turnover is low in type 2 diabetes and the increased BMD does not explain the increased fracture risk. However, the low bone turnover may lead to insufficient bone renewal with unrepaired micro-cracks and thus increase fracture risk. Ingestion of food acutely decreases bone resorption markers and the macronutrient composition of meals and meal frequency may influence bone metabolism adversely in subjects with unhealthy eating patterns, e.g., patients with type 2 diabetes.

AREAS COVERED

The treatment strategy of bone disease in type 2 diabetics is covered in this review. The current management of diabetic bone disease consists of anti-osteoporotic treatment. However, anti-resorptives may further reduce an already low bone turnover with uncertain effects. Furthermore, the acute and long-term effects of meal ingestion, weight loss alone and in combination with exercise as well as the possible underlying mechanisms are covered in this systematic review.

EXPERT COMMENTARY

Current management of diabetic bone disease is based on principles of anti-osteoporotic treatment in non-diabetic subjects. However, studies are urged to investigate whether anti-resorptives are equally beneficial in type 2 diabetes as in non-diabetic individuals.

Relationship Between Changes in Fat and Lean Depots Following Weight Loss and Changes in Cardiovascular Disease Risk Markers

Background

Gluteofemoral fat mass has been associated with improved cardiovascular disease risk factors. It is not clear if loss of this protective fat during weight loss partially negates the effect of loss of visceral fat. The aim of this study was to examine regional fat loss in a large weight‐loss cohort from one center and to determine if fat loss in the leg and total lean tissue loss is harmful.

Methods and Results

We combined the data from 7 of our previously published 3‐month weight‐loss studies and examined the relationship between regional fat and lean tissue loss and changes in cardiovascular disease risk factors in 399 participants. At baseline, leg fat was positively associated with high‐density lipoprotein cholesterol in women and inversely with fasting triglyceride level in both sexes. Abdominal lean tissue was also related to systolic blood pressure in men. Changes in regional fat and lean tissue were positively associated with changes in glucose, insulin, total cholesterol, triglycerides, low‐density lipoprotein cholesterol and systolic and diastolic blood pressure (r=0.11–0.22, P<0.05) with leg fat and arm lean tissue dominating in multivariate regression. After adjustment for total weight or total fat change, these relationships disappeared except for a positive relationship between arm and lean leg mass loss and changes in triglycerides and systolic blood pressure.

Conclusions

Loss of leg fat and leg lean tissue was directly associated with beneficial changes in cardiovascular disease risk markers. Loss of lean tissue may not have an adverse effect on cardiovascular disease risk, and measures to retain lean tissue during weight loss may not be necessary.

Overweight postmenopausal women with different plasma estradiol concentrations present with a similar pattern of energy expenditure and substrate oxidation rate before and after a fatty meal challenge

Menopause-related withdrawal of ovarian estrogens is associated with reduced energy metabolism and overall impairment of substrate oxidation. Estradiol's withdrawal after menopause is associated with a reduction in energy metabolism and impaired substrate oxidation, which contributes to weight gain and visceral fat accumulation. Here we aimed to investigate the association between plasma estradiol concentrations and energy expenditure (EE)/substrate oxidation in a group of overweight postmenopausal women before and after a fatty meal challenge. Women were divided into three groups according to their plasma estradiol concentrations (E2): group 1 - E₂ ≤ 39, group 2 - 40 ≤ E₂ ≤ 59, and group 3 - E₂ ≥ 60 pg/mL. VO₂ and VCO₂ volumes were collected following indirect calorimetry 5 h following a single lipid overload meal (1100 kcal, 72% of fat). For comparisons between groups and within the same group, a linear regression model with mixed effects was applied (P < 0.05). Forty-four women aged 55 ± 0.7 years-old, 8 ± 1.1 years following menopause, with a BMI of 30.5 ± 0.5 kg/m², and 41.9 ± 0.7% of body fat were enrolled the study. Plasma E2 concentrations were: group 1 - 30.4 ± 1.9, group 2 - 46.9 ± 1.5, and group 3 - 91.3 ± 12.0 pg/mL (P < 0.0001). EE at baseline and in the resting state was 1320 ± 24.3 kcal/d, and increased to 1440 ± 27.0 kcal/d 30 min following ingestion of the fatty meal (P < 0.0001), and rose again to an average of 1475 ± 30.3 kcal/d at the completion of experiment (P < 0.0001). Carbohydrate oxidation (Chox) was 0.155 ± 0.01 g/min at resting, maintained as 0.133 ± 0.00 g/min 30 min after ingestion of the fatty meal, and was 0.123 ± 0.01 g/min at the end of the testing period. Lipid oxidation (Lipox) was 0.041 ± 0.003 g/min at resting, increasing to 0.054 ± 0.003 g/min at 30 min (P = 0.01), and reaching 0.063 ± 0.003 g/min at the end of the experiment (P < 0.0001). There was no difference between groups for EE, Chox or Lipox. Our data suggest that EE and substrate oxidation were modulated following a lipid-meal challenge equally in all groups and this did not differ with plasma E2 concentrations.

Short term elevation in dietary protein intake does not worsen insulin resistance or lipids in older adults with metabolic syndrome: a randomized-controlled trial

Background

There is a great deal of controversy as to whether higher protein intake improves or worsens insulin sensitivity in humans. The purpose of the study was to determine the influence of a short-term elevation in dietary protein on hepatic and peripheral insulin sensitivity in twelve older subjects (51–70 yrs) with metabolic syndrome.

Methods

Individuals were randomly assigned to one of the dietary groups: recommended protein intake (RPI, 10% of daily calorie intake) or elevated protein intake (EPI, 20% of daily calorie intake) for 4 weeks. Prior to and immediately following the dietary intervention, subjects were studied with primed continuous infusion of [6,6-²H₂]glucose and [1-¹³C]glucose dissolved in drink during the dual tracer oral glucose tolerance test (DT OGTT) to determine hepatic and peripheral insulin sensitivity. Plasma lipids were measured pre- and post-dietary intervention.

Results

In both intervention groups: 1) hepatic insulin sensitivity as assessed by the endogenous glucose rate of appearance (glucose R_a), 2) peripheral insulin sensitivity as assessed by the metabolic clearance rate of glucose normalized to plasma glucose concentration (MCR) and/or the rate of glucose utilization (R_d) or 3) glucose/insulin AUC were unaffected by the diets. Moreover, fasting lipid was not affected by RPI or EPI.

Conclusion

Our findings suggest that a short-term elevation in EPI with correspondingly higher branched chain amino acid (BCAA) contents has no detrimental impact on hepatic and peripheral insulin sensitivity or plasma lipid parameters in older adults with metabolic syndrome.

Trial registration

ClinicalTrials.gov Identifier: NCT02885935; This trial was registered retrospectively (Study start date, April 01, 2013, date of registration, August 26, 2016).

Electronic supplementary material

The online version of this article (doi:10.1186/s40795-017-0152-4) contains supplementary material, which is available to authorized users.

Effect of meal composition on postprandial lipid concentrations and lipoprotein particle numbers: A randomized cross-over study

Background

It is unclear how high-protein (HP) and high-monounsaturated fat (HMF) meals affect postprandial blood lipids and lipoprotein particle numbers (LPN).

Purpose

To compare a HP versus a HMF meal on postprandial lipid and LPN responses.

Methods

Twenty-four participants (age: 36.3±15.0 years; body mass index: 23.6±2.0 kg/m²; 45.8% female) were fed a HP (31.9% energy from protein) and a HMF (35.2% fat and 20.7% monounsaturated fat) meal in a randomized cross-over trial design. Energy and carbohydrate content were the same across meals. Blood samples were drawn in the fasting state and 3 hour postprandial state, and assessed for lipids and LPN.

Results

Repeated measures analysis showed a significant (p<0.05) treatment by time interaction effect for triglycerides (TG), the primary variable, total high-density lipoprotein particles (T-HDLP) and T-HDLP minus large-buoyant high-density lipoprotein 2b (T-HDLP—LB-HDL2b). HP versus HMF condition led to significantly lower TG at 120 (geometric mean: 90.1 (95% confidence interval (CI): 76.4–106.3) vs. 146.5 (124.2–172.9) mg/dL) and 180 (101.4 (83.1–123.8) vs. 148.7 (121.9–181.4) mg/dL) min and higher T-HDLP at 120 (mean difference: 297.3 (95% CI: 48.6–545.9) nmol/L) and 180 (291.6 (15.8–567.5) nmol/L) min. The difference in T-HDLP by condition was due to the significantly higher small-dense HDLP (T-HDLP—LB-HDL2b) during HP versus HMF condition at 120 (mean difference: 452.6 (95% CI: 177.4–727.9) nmol/L) and 180 (496.8 (263.1–730.6) nmol/L) min. Area under the curve analysis showed that HP versus HMF condition led to significantly lower TG, non-HDLP, and very-low-density lipoprotein particles (VLDLP) responses but significantly less favorable responses in LB-HDL2b particles, T-HDLP—LB-HDL2b, and LB-HDL2b/T-HDLP ratio.

Conclusion

The HP meal led to lower TG, non-HDLP, and VLDLP but less favorable LB-HDL2b, small-dense HDLP, and LB-HDL2b/T-HDLP ratio responses versus a HMF meal. Further studies are needed to confirm these findings over multiple meals.

Energy compensation following consumption of sugar-reduced products: a randomized controlled trial

PURPOSE

Consumption of sugar-reformulated products (commercially available foods and beverages that have been reduced in sugar content through reformulation) is a potential strategy for lowering sugar intake at a population level. The impact of sugar-reformulated products on body weight, energy balance (EB) dynamics and cardiovascular disease risk indicators has yet to be established. The REFORMulated foods (REFORM) study examined the impact of an 8-week sugar-reformulated product exchange on body weight, EB dynamics, blood pressure, arterial stiffness, glycemia and lipemia.

METHODS

A randomized, controlled, double-blind, crossover dietary intervention study was performed with fifty healthy normal to overweight men and women (age 32.0 ± 9.8 year, BMI 23.5 ± 3.0 kg/m(2)) who were randomly assigned to consume either regular sugar or sugar-reduced foods and beverages for 8 weeks, separated by 4-week washout period. Body weight, energy intake (EI), energy expenditure and vascular markers were assessed at baseline and after both interventions.

RESULTS

We found that carbohydrate (P < 0.001), total sugars (P < 0.001) and non-milk extrinsic sugars (P < 0.001) (% EI) were lower, whereas fat (P = 0.001) and protein (P = 0.038) intakes (% EI) were higher on the sugar-reduced than the regular diet. No effects on body weight, blood pressure, arterial stiffness, fasting glycemia or lipemia were observed.

CONCLUSIONS

Consumption of sugar-reduced products, as part of a blinded dietary exchange for an 8-week period, resulted in a significant reduction in sugar intake. Body weight did not change significantly, which we propose was due to energy compensation.

Effects of dietary protein intake on body composition changes after weight loss in older adults: a systematic review and meta-analysis

CONTEXT

The impact of dietary protein on body composition changes after older adults purposefully lose weight requires systematic evaluation

OBJECTIVE

: This systematic review and meta-analysis assessed the effects of protein intake (< 25% vs ≥ 25% of energy intake or 1.0 g/kg/d) on energy restriction-induced changes in body mass, lean mass, and fat mass in adults older than 50 years.

DATA SOURCES

PubMed, Cochrane, Scopus, and Google Scholar were searched using the keywords "dietary proteins," "body composition," "skeletal muscle," and "muscle strength."

STUDY SELECTION

Two researchers independently screened 1542 abstracts.

DATA EXTRACTION

Information was extracted from 24 articles.

DATA SYNTHESIS

Twenty randomized control trials met the inclusion criteria.

CONCLUSION

Older adults retained more lean mass and lost more fat mass during weight loss when consuming higher protein diets.

Plasma Free Amino Acid Responses to Intraduodenal Whey Protein, and Relationships with Insulin, Glucagon-Like Peptide-1 and Energy Intake in Lean Healthy Men

This study determined the effects of increasing loads of intraduodenal (ID) dairy protein on plasma amino acid (AA) concentrations, and their relationships with serum insulin, plasma glucagon-like peptide-1 (GLP-1) and energy intake. Sixteen healthy men had concentrations of AAs, GLP-1 and insulin measured in response to 60-min ID infusions of hydrolysed whey protein administered, in double-blinded and randomised order, at 2.1 (P2.1), 6.3 (P6.3) or 12.5 (P12.5) kJ/min (encompassing the range of nutrient emptying from the stomach), or saline control (C). Energy intake was quantified immediately afterwards. Compared with C, the concentrations of 19/20 AAs, the exception being cysteine, were increased, and this was dependent on the protein load. The relationship between AA concentrations in the infusions and the area under the curve from 0 to 60 min (AUC0-60 min) of each AA profile was strong for essential AAs (R² range, 0.61-0.67), but more variable for non-essential (0.02-0.54) and conditional (0.006-0.64) AAs. The AUC0-60 min for each AA was correlated directly with the AUC0-60 min of insulin (R² range 0.3-0.6), GLP-1 (0.2-0.6) and energy intake (0.09-0.3) (p < 0.05, for all), with the strongest correlations being for branched-chain AAs, lysine, methionine and tyrosine. These findings indicate that ID whey protein infused at loads encompassing the normal range of gastric emptying increases plasma concentrations of 19/20 AAs in a load-dependent manner, and provide novel information on the close relationships between the essential AAs, leucine, valine, isoleucine, lysine, methionine, and the conditionally-essential AA, tyrosine, with energy intake, insulin and GLP-1.

Acute load-dependent effects of oral whey protein on gastric emptying, gut hormone release, glycemia, appetite, and energy intake in healthy men

BACKGROUND

In healthy individuals, intraduodenal whey protein load-dependently modulates gastrointestinal motor and hormonal functions and suppresses energy intake. The effect of oral whey, particularly the impact of load, has not been evaluated.

OBJECTIVE

The purpose of this study was to quantify gastric emptying of 30 and 70 g of oral whey protein loads and their relation to gastrointestinal hormone, glycemic, and appetitive responses.

DESIGN

On 3 separate occasions in a randomized, double-blind order, 18 lean men [mean ± SEM age: 24.8 ± 1.4 y; body mass index (in kg/m(2)): 21.6 ± 0.5] received iso-osmolar, equally palatable drinks (∼450 mL) containing 30 g pure whey protein isolate (L), 70 g pure whey protein isolate (H), or saline (control). Gastric emptying (with the use of 3-dimensional ultrasound), plasma cholecystokinin, glucagon-like peptide 1, glucose-dependent insulinotropic peptide, insulin, glucagon, total amino acids, and blood glucose were measured for 180 min after consumption of the drinks, and energy intake at a buffet-style lunch was quantified.

RESULTS

Gastric emptying of the L and H drinks was comparable when expressed in kilocalories per minute (L: 2.6 ± 0.2 kcal/min; H: 2.9 ± 0.3 kcal/min) and related between individuals (r = 0.54, P < 0.01). Gastrointestinal hormone, insulin, and glucagon responses to the L and H drinks were comparable until ∼45-60 min after ingestion, after which time the responses became more differentiated. Blood glucose was modestly reduced after the H drink between t = 45 and 150 min when compared with the L drink (all P < 0.05). Energy intake was suppressed by both L and H drinks compared with control (P < 0.05) (control: 1174 ± 91 kcal; L: 1027 ± 81 kcal; and H: 997 ± 71 kcal).

CONCLUSION

These findings indicate that, in healthy lean men, the rate of gastric emptying of whey protein is independent of load and determines the initial gastrointestinal hormone response. This study was registered at www.anzctr.org.au as 12611000706976.

Effectiveness of weight loss interventions--is there a difference between men and women: a systematic review

Effective strategies are required to reduce the prevalence of overweight and obesity; however, the effectiveness of current weight loss programmes is variable. One contributing factor may be the difference in weight loss success between men and women. A systematic review was conducted to determine whether the effectiveness of weight loss interventions differs between men and women. Randomized controlled trials published up until March 2014 were included. Effect sizes (Hedges' g) were used to examine the difference in weight outcomes between men and women. A total of 58 studies met the eligibility criteria with 49 studies of higher quality included in the final data synthesis. Eleven studies that directly compared weight loss in men and women reported a significant sex difference. Ten of these reported that men lost more weight than women; however, women also lost a significant amount of weight. Analysis of effect sizes found small differences in weight loss favouring men for both diet (g = 0.489) and diet plus exercise (g = 0.240) interventions. There is little evidence from this review to indicate that men and women should adopt different weight loss strategies. Current evidence supports moderate energy restriction in combination with exercise for weight loss in both men and women.

Diets high in protein or saturated fat do not affect insulin sensitivity or plasma concentrations of lipids and lipoproteins in overweight and obese adults

BACKGROUND

Previous human studies reported inconsistent effects of dietary protein and branched-chain amino acids (BCAAs) on insulin action and glucose metabolism. Similarly, it is unclear whether saturated fat (SF) intake influences these metabolic variables.

OBJECTIVE

The objective of this study was to test the effects of high [30% of energy (%E)] vs. moderate (20%E) intakes of protein (primarily whey) on insulin action and lipid and lipoprotein concentrations in the context of both high (15%E) and low (7%E) SF diets.

METHODS

The study was conducted as a randomized controlled trial in 158 overweight and obese men and women. After a 4-wk baseline diet [55%E carbohydrate, 15%E protein, 30%E fat (7%E SF)], participants were randomly assigned to 4 wk of either the baseline diet or 1 of 4 test diets containing 35%E carbohydrate and either 20%E or 30%E protein and either 7%E or 15%E SF. Frequently sampled i.v. glucose tolerance tests were administered after each dietary period.

RESULTS

Other than significantly higher fasting glucose concentrations for high vs. moderate protein intakes with a low-fat diet (difference ± SE: 0.47 ± 0.14 mmol/L; P = 0.001), there were no significant effects of dietary protein or SF on glucose metabolism, plasma insulin, or concentrations of lipids and lipoproteins. Changes in plasma BCAAs across all diets were negatively correlated with changes in the metabolic clearance rate of insulin (ρ = -0.18, P = 0.03) and positively correlated with changes in the acute insulin response to glucose (ρ = 0.15, P = 0.05).

CONCLUSIONS

These findings suggest that short-term intake of BCAAs can influence insulin dynamics. However, in this group of overweight and obese individuals, neither high protein nor SF intake affected insulin sensitivity or plasma concentrations of lipids and lipoproteins. This trial was registered at clinicaltrials.gov as NCT00508937.

Lifestyle interventions for cardiovascular disease risk reduction: a systematic review of the effects of diet composition, food provision, and treatment modality on weight loss

The purpose of this systematic review was to evaluate, synthesize, and interpret findings from recent randomized controlled trials (RCTs) of dietary and lifestyle weight loss interventions examining the effects of (1) diet composition, (2) use of food provision, and (3) modality of treatment delivery on weight loss. Trials comparing different dietary approaches indicated that reducing carbohydrate intake promoted greater initial weight loss than other approaches but did not appear to significantly improve long-term outcomes. Food provision appears to enhance adherence to reduction in energy intake and produce greater initial weight losses. The long-term benefits of food provision are less clear. Trials comparing alternative treatment modalities suggest that phone-based treatment produce short- and long-term weight reductions equivalent to face-to-face interventions. The use of Internet and mobile technologies are associated with smaller reductions in body weight than face-to-face interventions. Based on this review, clinical implications and future research directions are provided.

Low carbohydrate versus isoenergetic balanced diets for reducing weight and cardiovascular risk: a systematic review and meta-analysis

BACKGROUND

Some popular weight loss diets restricting carbohydrates (CHO) claim to be more effective, and have additional health benefits in preventing cardiovascular disease compared to balanced weight loss diets.

METHODS AND FINDINGS

We compared the effects of low CHO and isoenergetic balanced weight loss diets in overweight and obese adults assessed in randomised controlled trials (minimum follow-up of 12 weeks), and summarised the effects on weight, as well as cardiovascular and diabetes risk. Dietary criteria were derived from existing macronutrient recommendations. We searched Medline, EMBASE and CENTRAL (19 March 2014). Analysis was stratified by outcomes at 3-6 months and 1-2 years, and participants with diabetes were analysed separately. We evaluated dietary adherence and used GRADE to assess the quality of evidence. We calculated mean differences (MD) and performed random-effects meta-analysis. Nineteen trials were included (n = 3209); 3 had adequate allocation concealment. In non-diabetic participants, our analysis showed little or no difference in mean weight loss in the two groups at 3-6 months (MD 0.74 kg, 95%CI -1.49 to 0.01 kg; I2 = 53%; n = 1745, 14 trials; moderate quality evidence) and 1-2 years (MD 0.48 kg, 95%CI -1.44 kg to 0.49 kg; I2 = 12%; n = 1025; 7 trials, moderate quality evidence). Furthermore, little or no difference was detected at 3-6 months and 1-2 years for blood pressure, LDL, HDL and total cholesterol, triglycerides and fasting blood glucose (>914 participants). In diabetic participants, findings showed a similar pattern.

CONCLUSIONS

Trials show weight loss in the short-term irrespective of whether the diet is low CHO or balanced. There is probably little or no difference in weight loss and changes in cardiovascular risk factors up to two years of follow-up when overweight and obese adults, with or without type 2 diabetes, are randomised to low CHO diets and isoenergetic balanced weight loss diets.

A randomized controlled trial to evaluate the effect of incorporating peanuts into an American Diabetes Association meal plan on the nutrient profile of the total diet and cardiometabolic parameters of adults with type 2 diabetes

Background

According to the American Diabetes Association (ADA), the nutritional goals for patients with type 2 diabetes (T2D) are to achieve an optimal nutrient intake to achieve normoglycemia and a cardioprotective lipid profile. Peanuts are nutrient dense foods that contain high levels of monounsaturated fat (MUFA) and are a natural source of arginine, fiber, phytosterols, resveritrol, niacin, folate, vitamin E and magnesium, which have the potential for improving blood lipids and glycemic control. This study sought to evaluate the effect of a peanut enriched ADA meal plan on the nutrient profile of the total diet and cardiometabolic parameters in adults with T2D.

Methods

This was a randomized, prospective 24-week parallel-group clinical trial with 60 adults with T2D [age range 34–84 years; body mass index (BMI) range 17.2-48.7 kg/m²]. Subjects consumed an ADA meal plan containing ~20% of energy from peanuts (peanut group) or a peanut-free ADA meal plan (control group). Weight, BMI, waist circumference (WC) and nutrient intake from 24-hour recalls were measured every 4 weeks and fasting blood glucose (FBG), HbA1c and blood lipids were measured every 12 weeks. A mixed-model repeated-measures analysis of covariance was performed to assess the significance of changes in the cardiometabolic parameters.

Results

A higher polyunsaturated fat (PUFA) to saturated fat diet ratio and higher intake of MUFA, PUFA, α-tocopherol, niacin and magnesium was observed in the peanut group as compared to the control group (P < 0.01-P = 0.04). Both groups experienced mild reductions in weight, BMI, and WC during the study (P = 0.01-P = 0.03), however there were no differences between the two groups in these measurements or in FBG, HbA1c or blood lipids. For each kilogram of weight loss in the entire cohort there were associations for reductions in WC of 0.48 cm (P < 0.01), FBG of 0.11 mmol/l (P = 0.01) and HbA1c of 0.07% (P < 0.01).

Conclusions

Daily consumption of a peanut enriched (46 g/d) ADA meal plan over 24 weeks improves the nutrient profile of the total diet and is compatible with weight management and improvement in specific blood lipids.

Trial registration

ClinicalTrials.gov NCT00937222

Impact of weight loss and maintenance with ad libitum diets varying in protein and glycemic index content on metabolic syndrome

OBJECTIVES

We investigated the effects of weight loss and maintenance with diets that varied with regard to protein content and glycemic index (GI) on metabolic syndrome (MetSyn) status.

METHODS

Secondary analyses were performed within the Diet, Obesity and Genes (DiOGenes) study (2006-2008), a randomized controlled dietary intervention. Nine hundred and thirty-eight overweight and obese adults from eight European countries entered an 8-wk low-calorie-diet period. Seven hundred and seventy-three adults who lost at least 8% of their body weights were randomized to one of five ad libitum diets for 6 mo: 1) low-protein (LP)/low-GI (LGI); 2) LP/high-GI (HGI); 3) high-protein (HP)/LGI; 4) HP/HGI; and 5) control diet. MetSyn prevalence and a standardized MetSyn score were assessed at baseline, after the low-calorie diet, and after the intervention.

RESULTS

Weight loss among participants while on the low-calorie diet significantly reduced MetSyn prevalence (33.9% versus 15.9%; P < 0.001) and MetSyn score (-1.48 versus -4.45; P < 0.001). During weight maintenance, significant changes in MetSyn score were observed between the groups, with the highest increase detected in the LP/HGI group (P = 0.039, partial η(2) = 0.023). Protein, GI, and their interaction did not have isolated effects on study outcomes.

CONCLUSIONS

Neither protein nor GI affected MetSyn status in this sample of European overweight and obese adults. However, a diet with a combination of an increased protein-to-carbohydrate ratio with low-GI foods had beneficial effects on MetSyn factors.

Is there an optimal diet for patients with type 2 diabetes? Yes, the one that works for them!

Diet is fundamental in the aetiology and management of type 2 diabetes. The optimal diet remains unclear and the EASD and ADA have recently adopted increased flexibility with dietary composition, whilst maintaining a focus on reduced energy, reduced saturated fat and increased dietary fibre. This review draws three conclusions on the current evidence for three dietary approaches; high protein diets, very low carbohydrate diets and the Mediterranean diet, specifically for the management of weight, glycaemic control and cardiovascular risk in patients with type 2 diabetes. First, unless energy intake is reduced below energy expenditure over a sustained period of time, weight loss will not occur. Second, weight loss achieved with any dietary approach over the long-term is modest, though compared with the natural history of weight gain in obesity is clinically important. Third, the evidence supports flexibility in dietary composition with no approach superior to another for weight loss, glycaemic control or cardiovascular risk management. Most importantly there is evidence that adherence to any given dietary approach is more important than the macronutrient prescription. So the best diet for those with type 2 diabetes is the one that works for them, and critically the one that they can maintain in the long term.

Normal vs. high-protein weight loss diets in men: effects on body composition and indices of metabolic syndrome

OBJECTIVE

This study assessed the effectiveness of a prescribed weight-loss diet with 0.8 versus 1.4 g protein·kg(-1) day(-1) on changes in weight, body composition, indices of metabolic syndrome, and resting energy expenditure (REE) in overweight and obese men.

DESIGN AND METHODS

Men were randomized to groups that consumed diets containing 750 kcal day(-1) less than daily energy needs for weight maintenance with either normal protein (NP, n = 21) or higher protein (HP, n = 22) content for 12 weeks. The macronutrient distributions of the NP and HP diets were 25:60:15, and 25:50:25 percent energy from fat, carbohydrate, and protein, respectively. Assessments were made pre and post intervention. The subjects were retrospectively subgrouped into overweight and obese groups.

RESULTS AND CONCLUSION

Both diet groups lost comparable body weight and fat. The HP group lost less lean body mass than the NP group (-1.9 ± 0.3 vs. -3.0 ± 0.4 kg). The effects of protein and BMI status on lean body mass loss were additive. The reductions in total cholesterol, HDL-C, triacylglycerol, glucose, and insulin, along with LDL-C, total cholesterol-to-HDL-C ratio, and HOMA-IR, were not statistically different between NP and HP. Likewise, macronutrient distributions of the diet did not affect the reductions in REE, and blood pressure. In conclusion, energy restriction effectively improves multiple clinical indicators of cardiovascular health and glucose control, and consumption of a higher-protein diet and accomplishing weight loss when overweight versus obese help men preserve lean body mass over a short period of time.

Effect of a High Protein Weight Loss Diet on Weight, High-Sensitivity C-Reactive Protein, and Cardiovascular Risk among Overweight and Obese Women: A Parallel Clinical Trial

Studies regarding the effects of high protein (HP) diets on cardiovascular (CVD) risk factors have reported contradictory results. We aimed to determine the effects of an HP diet on CVD risk factors and high-sensitivity C-reactive protein (hs-CRP) among overweight and obese women. In this randomized controlled trial, we recruited 60 overweight and obese women, aged 20-65, into an HP or energy-restricted control diet for three months (protein, carbohydrate, and fat: 25%, 45%, and 30% versus 15%, 55%, and 30%, resp.). Total protein was divided between animal and plant sources in a 1 : 1 ratio, and animal sources were distributed equally between meats and dairy products. Fasting blood samples, hs-CRP, lipid profile, systolic and diastolic blood pressure, and anthropometric measurements were assessed using standard guidelines. Percent change was significantly different between the two diet groups for weight (standard protein (SP): -3.90 ± 0.26 versus HP: -6.10 ± 0.34%; P < 0.0001, resp.) and waist circumference (SP: -3.03 ± 0.21 versus HP: -5.06 ± 0.28%; P < 0.0001, resp.). Percent change of fasting blood glucose (FBG) substantially decreased in the control group compared to the HP group (-9.13 ± 0.67 versus -4.93 ± 1.4%; P = 0.01, resp.). Total cholesterol, systolic blood pressure (SBP), and diastolic blood pressure (DBP) decreased both in the HP and in the control diet groups (P = 0.06, P = 0.07, and P = 0.09, resp.); however, the results were marginally significant. Serum levels of hs-CRP were reduced both in the control (-0.08 ± 0.11%, P = 0.06) and in the high protein groups (-0.04 ± 0.09%, P = 0.06). The energy-restricted HP diet resulted in more beneficial effects on weight loss and reduction of waist circumference. CVD risk factors may improve with HP diets among overweight and obese women. When using isoenergetic weight loss diets, total cholesterol, hs-CRP, and SBP were marginally significantly reduced, independent of dietary protein content. This trial is registered with ClinicalTrials.gov NCT01763528.

Alternate day fasting (ADF) with a high-fat diet produces similar weight loss and cardio-protection as ADF with a low-fat diet

Alternate day fasting (ADF) with a low-fat (LF) diet is effective for weight loss and cardio-protection. However, the applicability of these findings is questionable as the majority of Americans consume a high-fat (HF) diet.

OBJECTIVE

The goal of this study was to determine if these beneficial changes in body weight and coronary heart disease (CHD) risk can be reproduced if an HF background diet is used in place of an LF diet during ADF.

METHODS

Thirty-two obese subjects were randomized to an ADF-HF (45% fat) or ADF-LF diet (25% fat), which consisted of two phases: 1) a 2-week baseline weight maintenance period, and 2) an 8-week ADF weight loss period. All food was provided during the study.

RESULTS

Body weight was reduced (P<0.0001) by ADF-HF (4.8%±1.1%) and by ADF-LF (4.2%±0.8%). Fat mass decreased (P<0.0001) by ADF-HF (5.4±1.5 kg) and ADF-LF (4.2±0.6 kg). Fat free mass remained unchanged. Waist circumference decreased (P<0.001) by ADF-HF (7.2±1.5 cm) and ADF-LF (7.3±0.9 cm). LDL cholesterol and triacylglycerol concentrations were reduced (P<0.001) by both interventions (ADF-HF: 18.3%±4.6%, 13.7%±4.8%; and ADF-LF: 24.8%±2.6%, 14.3%±4.4%). HDL cholesterol, blood pressure, and heart rate remained unchanged. There were no between-group differences for any parameter.

CONCLUSION

These findings suggest that an ADF-HF diet is equally as effective as an ADF-LF diet in helping obese subjects lose weight and improve CHD risk factors.

Obesity management in women with polycystic ovary syndrome

Obesity and insulin resistance play an important role in initiating or maintaining ill health in polycystic ovary syndrome (PCOS). This implies that treatment that reduces body weight and insulin resistance would alleviate the symptoms of PCOS. Lifestyle modification has been found to be effective in restoring reproductive function in up to 80% of individuals who achieve at least 5% weight loss. However, long-term weight maintenance is a challenge. This article provides a review of reduced glycemic load diets, including low glycemic index, very low carbohydrate, high-protein and high monounsaturated fat diets, on metabolic and reproductive health in PCOS and non-PCOS populations. Dietary trials in non-PCOS women suggest that higher-protein, reduced glycemic load diets were probably more beneficial than the conventional low-fat, high-carbohydrate diet but further studies are required to confirm this in PCOS women. Similarly, the optimal exercise regime for PCOS women remains to be investigated.

MTOR signaling and ubiquitin-proteosome gene expression in the preservation of fat free mass following high protein, calorie restricted weight loss

Caloric restriction is one of the most efficient ways to promote weight loss and is known to activate protective metabolic pathways. Frequently reported with weight loss is the undesirable consequence of fat free (lean muscle) mass loss. Weight loss diets with increased dietary protein intake are popular and may provide additional benefits through preservation of fat free mass compared to a standard protein, high carbohydrate diet. However, the precise mechanism by which a high protein diet may mitigate dietary weight loss induced reductions in fat free mass has not been fully elucidated. Maintenance of fat free mass is dependent upon nutrient stimulation of protein synthesis via the mTOR complex, although during caloric restriction a decrease (atrophy) in skeletal muscle may be driven by a homeostatic shift favouring protein catabolism. This review evaluates the relationship between the macronutrient composition of calorie restricted diets and weight loss using metabolic indicators. Specifically we evaluate the effect of increased dietary protein intake and caloric restricted diets on gene expression in skeletal muscle, particularly focusing on biosynthesis, degradation and the expression of genes in the ubiquitin-proteosome (UPP) and mTOR signaling pathways, including MuRF-1, MAFbx/atrogin-1, mTORC1, and S6K1.

Intraduodenal protein modulates antropyloroduodenal motility, hormone release, glycemia, appetite, and energy intake in lean men

BACKGROUND

Intraduodenal fat and carbohydrate modulate antropyloroduodenal motility and hormone release and suppress appetite and energy intake in a load-dependent manner. Protein also suppresses energy intake, but its effects on these gastrointestinal factors and their role in the appetite-suppressive effects of protein remain unclear.

OBJECTIVE

We aimed to characterize the effects of different intraduodenal protein loads on antropyloroduodenal pressures, gastrointestinal hormone release, glucose and insulin concentrations, appetite perceptions, and energy intake.

DESIGN

Sixteen lean, healthy men were studied on 4 occasions in a randomized, double-blind fashion. Antropyloroduodenal pressures, plasma glucagon-like peptide 1 (GLP-1), cholecystokinin, peptide YY, ghrelin, blood glucose, serum insulin, and appetite were measured during 60-min, 4-mL/min intraduodenal infusions of protein at 0.5, 1.5, or 3 kcal/min or saline (control). Energy intakes at a buffet lunch consumed immediately after the infusion were quantified.

RESULTS

Increases in the load of protein resulted in greater suppression of antral motility, greater stimulation of basal and isolated pyloric pressures and plasma cholecystokinin and GLP-1 concentrations, and greater suppression of energy intake. However, energy intake was reduced only after a protein load of 3 kcal/min compared with after all other treatments (P < 0.05). The suppression of energy intake after adjustment for cholecystokinin, GLP-1, and insulin was related inversely with basal pyloric pressure (r = -0.51, P < 0.001).

CONCLUSION

The acute effects of intraduodenal protein on antropyloroduodenal motility, gastrointestinal hormone release, glucose, and insulin are load dependent and contribute to the suppression of energy intake. This trial was registered at www.anzctr.org.au as 12610000376044.

Comparison of the effects of 52 weeks weight loss with either a high-protein or high-carbohydrate diet on body composition and cardiometabolic risk factors in overweight and obese males

BACKGROUND

A high-protein (HP), low-fat weight-loss diet may be advantageous for improving cardiometabolic health outcomes and body composition. To date, only limited research has been conducted in male participants.

OBJECTIVE

To evaluate the medium to long-term effects of two, low-fat, hypocaloric diets differing in carbohydrate:protein ratio on body composition and cardiometabolic health outcomes in overweight and obese males.

DESIGN

One hundred and twenty males (age 50.8±9.3 (s.d.) years, body mass index 33.0±3.9 kg m(-2)) were randomly assigned and consumed a low-fat, isocaloric, energy-restricted diet (7 MJ per day) with either HP (protein:carbohydrate:fat %energy, 35:40:25) or high carbohydrate (HC; 17:58:25). Body weight, body composition and cardiometabolic risk factors were assessed at baseline and after 12 and 52 weeks.

RESULTS

Sixty-eight participants completed the study (HP, n=33; HC, n=35). At 1 year both the groups experienced similar reductions in body weight (HP, -12.3±8.0 kg (-12%); HC, -10.9±8.6 kg (-11%); P=0.83 time × group interaction) and fat mass (-9.9±6.0 kg (-27%) vs -7.3±5.8 kg (-22%); P=0.11). Participants who consumed the HP diet lost less fat-free mass (-2.6±3.7 kg (-4%) vs -3.8±4.7 kg (-6%); P<0.01). Both groups experienced similar increases in high-density lipoprotein cholesterol (8%) and reductions in total cholesterol (-7%), low-density lipoprotein cholesterol (-9%), triglycerides (-24%), glucose (-3%), insulin (-38%), blood pressure (-7/-12%) and C-reactive protein (-29%), (P0.14).

CONCLUSION

In overweight and obese men, both a HP and HC diet reduced body weight and improved cardiometabolic risk factors. Consumption of a HP diet was more effective for improving body composition compared with an HC diet.

The effects of four hypocaloric diets containing different levels of sucrose or high fructose corn syrup on weight loss and related parameters

Background

The replacement of sucrose with HFCS in food products has been suggested as playing a role in the development of obesity as a public health issue. The objective of this study was to examine the effects of four equally hypocaloric diets containing different levels of sucrose or high fructose corn syrup (HFCS).

Methods

This was a randomized, prospective, double blind trial, with overweight/obese participants measured for body composition and blood chemistry before and after the completion of 12 weeks following a hypocaloric diet. The average caloric deficit achieved on the hypocaloric diets was 309 kcal.

Results

Reductions were observed in all measures of adiposity including body mass, BMI,% body fat, waist circumference and fat mass for all four hypocaloric groups, as well as reductions in the exercise only group for body mass, BMI and waist circumference.

Conclusions

Similar decreases in weight and indices of adiposity are observed when overweight or obese individuals are fed hypocaloric diets containing levels of sucrose or high fructose corn syrup typically consumed by adults in the United States.

Tailoring dietary approaches for weight loss

Although the ‘Low-Fat' diet was the predominant public health recommendation for weight loss and weight control for the past several decades, the obesity epidemic continued to grow during this time period. An alternative ‘low-carbohydrate' (Low-Carb) approach, although originally dismissed and even vilified, was comparatively tested in a series of studies over the past decade, and has been found in general to be as effective, if not more, as the Low-Fat approach for weight loss and for several related metabolic health measures. From a glass half full perspective, this suggests that there is more than one choice for a dietary approach to lose weight, and that Low-Fat and Low-Carb diets may be equally effective. From a glass half empty perspective, the average amount of weight lost on either of these two dietary approaches under the conditions studied, particularly when followed beyond 1 year, has been modest at best and negligible at worst, suggesting that the two approaches may be equally ineffective. One could resign themselves at this point to focusing on calories and energy intake restriction, regardless of macronutrient distributions. However, before throwing out the half-glass of water, it is worthwhile to consider that focusing on average results may mask important subgroup successes and failures. In all weight-loss studies, without exception, the range of individual differences in weight change within any particular diet groups is orders of magnitude greater than the average group differences between diet groups. Several studies have now reported that adults with greater insulin resistance are more successful with weight loss on a lower-carbohydrate diet compared with a lower-fat diet, whereas adults with greater insulin sensitivity are equally or more successful with weight loss on a lower-fat diet compared with a lower-carbohydrate diet. Other preliminary findings suggest that there may be some promise with matching individuals with certain genotypes to one type of diet over another for increasing weight-loss success. Future research to address the macronutrient intake component of the obesity epidemic should build on these recent insights and be directed toward effectively classifying individuals who can be differentially matched to alternate types of weight-loss diets that maximize weight-loss and weight-control success.

Dietary saturated fat intake is negatively associated with weight maintenance among the PREMIER participants

Research finding on the composition of macronutrient intakes on body weight has not been consistent. Furthermore, little research has examined the impact of subcomponents of macronutrients such as saturated fat or plant protein on body weight. The purpose of this report was to examine the impact of saturated fat, animal and plant protein, and other macronutrient intakes at the end of an intensive intervention on subsequent follow-up body weight. This is a secondary, observational data analysis using data from PREMIER, an 18-month randomized clinical trial that enrolled a total of 810 participants. Participants completed group and individual sessions designed to help them improve blood pressure (BP) control by making lifestyle changes. Dietary intakes were assessed by two 24-h diet recalls at baseline, 6, and 18 months. Body weight and physical fitness were monitored regularly. Regression models were used to examine the impact of animal or plant protein and other macronutrient intakes on subsequent body weight. After controlling for potential confounders, none of the calorie-contributing nutrient intakes at baseline was associated with subsequent weight at 6 or 18 months. However, a greater intake of saturated fat at 6 months was associated with higher weight at 18 months (P = 0.002). A greater intake of plant protein at 6 month was marginally associated with lower absolute weight at 18 month (P = 0.069). We conclude that macronutrient intakes before the intervention were not associated with subsequent body weight at 6 or 18 months. However, a lower saturated fat intake achieved after 6-month intervention predicts a lower body weight at 18 months and thus greater weight-loss maintenance.

Rate of weight loss can be predicted by patient characteristics and intervention strategies

BACKGROUND

Although dietary weight-loss counseling usually employs a 500 to 1,000 kcal/day energy deficit to induce weight loss of 0.5 to 1 kg/week, this rate of weight loss is rarely achieved in research settings. Biological factors, such as changes in metabolic rate, are partly responsible, but would only account for a small deviation from expected weight loss. There must be other factors, behavioral or related to study design and implementation, that affect the rate of weight loss observed.

OBJECTIVE

To examine factors that influence the rate of weight loss obtained in clinical studies.

DESIGN

Thirty-five weight-loss studies published between 1995 and 2009 were identified that used dietary counseling to induce weight loss in healthy subjects. Studies were included if they had a duration of at least 6 weeks, used a strategy to counsel subjects to reduce free-living energy intakes, and reported weight-loss data based on a completers analysis. Variables that were associated with the rate of weight loss among age, sex (percent female subjects), initial body weight, frequency of dietary counseling, placebo use, exercise level, study length, and prescribed energy deficit were examined using linear regression analysis.

RESULTS

Study length was negatively related to the rate of weight loss (P<0.0001), whereas subject age (P<0.002), subject age squared (P=0.0073), initial body weight (P=0.0003), frequency of dietary counseling (P=0.0197), and prescribed energy deficit (P<0.0001) were positively related to the rate of weight loss observed in clinical studies.

CONCLUSIONS

These findings provide a tool for investigators and clinical dietitians to predict the rate of weight loss that can be expected within a population given the age, initial body weight, frequency of dietary counseling, and energy deficit prescription. These data from clinical studies suggest that the rate of weight loss is greater in older and heavier subjects and with higher contact frequency and caloric restriction.

Chronologically scheduled snacking with high-protein products within the habitual diet in type-2 diabetes patients leads to a fat mass loss: a longitudinal study

BACKGROUND

Obesity is the most relevant overnutrition disease worldwide and is associated to different metabolic disorders such as insulin resistance and type-2 diabetes. Low glycemic load foods and diets and moderately high protein intake have been shown to reduce body weight and fat mass, exerting also beneficial effects on LDL-cholesterol, triglyceride concentrations, postprandial glucose curve and HDL-cholesterol levels. The present study aimed at studying the potential functionality of a series of low glycemic index products with moderately high protein content, as possible coadjuvants in the control of type-2 diabetes and weight management following a chronologically planned snacking offer (morning and afternoon).

METHODS

The current trial followed a single group, sequential, longitudinal design, with two consecutive periods of 4 weeks each. A total of 17 volunteers participated in the study. The first period was a free living period, with volunteers' habitual ad libitum dietary pattern, while the second period was a free-living period with structured meal replacements at breakfast, morning snack and afternoon snack, which were exchanged by specific products with moderately high protein content and controlled low glycemic index, following a scheduled temporal consumption. Blood extractions were performed at the beginning and at the end of each period (free-living and intervention). Parameters analysed were: fasting glucose, insulin, glycosylated hemoglobin, total-, HDL- and LDL-cholesterol, triglyceride, C - reactive protein and Homocysteine concentrations. Postprandial glucose and insulin were also measured. Anthropometrical parameters were monitored each 2 weeks during the whole study.

RESULTS

A modest but significant (p = 0.002) reduction on body weight (1 kg) was observed during the intervention period, mainly due to the fat mass loss (0.8 kg, p = 0.02). This weight reduction was observed without apparently associated changes in total energy intake. None of the biochemical biomarkers measured was altered throughout the whole study.

CONCLUSIONS

Small changes in the habitual dietary recommendations in type-2 diabetes patients by the inclusion of specific low-glycemic, moderately high-protein products in breakfast, morning and afternoon snacks may promote body weight and fat-mass loss, without apparently altering biochemical parameters and cardiovascular risk-related factors.

TRIAL REGISTRATION

Trial registered at clinicaltrials.gov NCT01264523.

Comparison of high protein and high fiber weight-loss diets in women with risk factors for the metabolic syndrome: a randomized trial

BACKGROUND

Studies have suggested that moderately high protein diets may be more appropriate than conventional low-fat high carbohydrate diets for individuals at risk of developing the metabolic syndrome and type 2 diabetes. However in most such studies sources of dietary carbohydrate may not have been appropriate and protein intakes may have been excessively high. Thus, in a proof-of-concept study we compared two relatively low-fat weight loss diets - one high in protein and the other high in fiber-rich, minimally processed cereals and legumes - to determine whether a relatively high protein diet has the potential to confer greater benefits.

METHODS

Eighty-three overweight or obese women, 18-65 years, were randomized to either a moderately high protein (30% protein, 40% carbohydrate) diet (HP) or to a high fiber, relatively high carbohydrate (50% carbohydrate, > 35 g total dietary fiber, 20% protein) diet (HFib) for 8 weeks. Energy intakes were reduced by 2000 - 4000 kJ per day in order to achieve weight loss of between 0.5 and 1 kg per week.

RESULTS

Participants on both diets lost weight (HP: -4.5 kg [95% confidence interval (CI):-3.7, -5.4 kg] and HFib: -3.3 kg [95% CI: -4.2, -2.4 kg]), and reduced total body fat (HP: -4.0 kg [5% CI:-4.6, -3.4 kg] and HFib: -2.5 kg [95% CI: -3.5, -1.6 kg]), and waist circumference (HP: -5.4 cm [95% CI: -6.3, -4.5 cm] and HFib: -4.7 cm [95% CI: -5.8, -3.6 cm]), as well as total and LDL cholesterol, triglycerides, fasting plasma glucose and blood pressure. However participants on HP lost more body weight (-1.3 kg [95% CI: -2.5, -0.1 kg; p = 0.039]) and total body fat (-1.3 kg [95% CI: -2.4, -0.1; p = 0.029]). Diastolic blood pressure decreased more on HP (-3.7 mm Hg [95% CI: -6.2, -1.1; p = 0.005]).

CONCLUSIONS

A realistic high protein weight-reducing diet was associated with greater fat loss and lower blood pressure when compared with a high carbohydrate, high fiber diet in high risk overweight and obese women.

A comparison of normal versus low dietary carbohydrate intake on substrate oxidation during and after moderate intensity exercise in women

We compared the effects of consuming a 2-day low-carbohydrate (CHO) diet (low-CHO; 20% CHO, 40% protein, 40% fat) versus an isocaloric 2-day moderate-CHO diet (mod-CHO; 55% CHO, 15% protein, 30% fat) on substrate oxidation during and after exercise in ten active, young women. Subjects were 24.9 ± 6.2% body fat with a VO(2max) of 68.8 ± 13.8 ml/kg FFM/min. For 2 days prior to exercise, subjects consumed either the mod-CHO or the low-CHO diet and then completed treadmill exercise at 55% of VO(2max) until 350 kcal of energy was expended. During exercise and for 2 h post-exercise, expired gases were analyzed to determine oxidation rates for CHO (CHO-OX) and fat (FAT-OX). Significant differences (p < 0.05) were found between diets for CHO-OX and FAT-OX (mg/kg FFM/min) during exercise, 1 h post-ex, and 2 h post-ex. During exercise, FAT-OX was higher (low-CHO 8.7 ± 2.2 vs. mod-CHO 6.2 ± 2.2) and CHO-OX was lower (low-CHO 25.1 ± 5.6 vs. mod-CHO 31.1 ± 6.2) following the low-CHO diet. A similar trend was observed during 1 h post-ex for FAT-OX (low-CHO 2.2 ± 0.5 vs. mod-CHO 1.6 ± 0.5) and CHO-OX (low-CHO 2.5 ± 1.2 vs. mod-CHO 4.1 ± 1.9), as well as 2 h post-ex for FAT-OX (low-CHO vs. 1.9 ± 0.5 mod-CHO 1.7 ± 0.4) and CHO-OX (low-CHO 2.5 ± 0.9 vs. mod-CHO 3.1 ± 1.1). Significant positive correlations were observed between VO(2max) and CHO-OX during exercise and post-exercise, as well as significant negative correlations between VO(2max) and FAT-OX post-exercise in the low-CHO condition. Waist circumference and FAT-OX exhibited a significant negative correlation during exercise in the low-CHO condition. Dietary macronutrient intake influenced substrate oxidation in active young women during and after moderate intensity exercise.

Polycystic ovary syndrome and weight management

Polycystic ovary syndrome (PCOS) is a common condition in women of reproductive age, and has reproductive, metabolic and psychological implications. Weight gain and obesity worsen the features of PCOS, while weight loss improves the features of PCOS. While there are potential barriers to successful weight management in young women who do not suffer from PCOS, women with PCOS may experience additional barriers. Weight management strategies in younger women with or without PCOS should encompass both the prevention of excess weight gain and achieving and maintaining a reduced weight through multidisciplinary lifestyle management, comprising dietary, exercise and behavioral therapy, as well as attention to psychosocial stress and practical and physiological barriers to weight management. Further research is warranted in the examination of specific barriers to weight management in women with PCOS, as well as in the determination of optimal components of lifestyle weight management interventions in young women in order to facilitate long-term compliance.

A high-protein low-fat diet is more effective in improving blood pressure and triglycerides in calorie-restricted obese individuals with newly diagnosed type 2 diabetes

BACKGROUND/OBJECTIVES

There is controversy over dietary protein's effects on cardiovascular disease risk factors in diabetic subjects. It is unclear whether observed effects are due to increased protein or reduced carbohydrate content of the consumed diets. The aim of this study was to compare the effects of two diets differing in protein to fat ratios on cardiovascular disease risk factors.

SUBJECTS/METHODS

A total of 17 obese (body mass index (BMI) ranging from 31 to 45 kg/m(2)) volunteers with type 2 diabetes (DM2), aged 46+/-3 years, consumed two diets, each for 4 weeks, with 3 weeks of washout period in a random, blind, crossover design. The diets were: (1) a high-protein low-fat diet (HP-LF, with 30% protein, 50% carbohydrates and 20% fat) and (2) a low-protein high-fat diet (LP-HF, with 15% protein, 50% carbohydrates and 35% fat). Their effects on fasting glycemic control, lipid levels and blood pressure, and on postprandial glucose and insulin responses after a standard test meal at the beginning and end of each dietary intervention were analyzed.

RESULTS

Both diets were equally effective in promoting weight loss and fat loss and in improving fasting glycemic control, total cholesterol and low-density lipoprotein (LDL) cholesterol, but the HP-LF diet decreased to a greater extent triglyceride (TG) levels (P=0.04) when compared with the LP-HF diet. HP-LF diet improved significantly both systolic and diastolic blood pressure when compared with the LP-HF diet (P<0.001 and P<0.001, respectively). No differences were observed in postprandial glucose and insulin responses.

CONCLUSIONS

A protein to fat ratio of 1.5 in diets significantly improves blood pressure and TG concentrations in obese individuals with DM2.

A high protein low fat meal does not influence glucose and insulin responses in obese individuals with or without type 2 diabetes

BACKGROUND

When substituted for carbohydrate in a meal, dietary protein enhances glycaemic control in subjects with type 2 diabetes (DM2). It is unknown whether the effect is a result of increased protein or reduced carbohydrate. The present study aimed to compare the effects of two meals differing in protein to fat ratios on post-prandial glucose and insulin responses.

METHODS

This was a crossover, blind study in which obese subjects with (n = 23) and without (n = 26) DM2 consumed two meals in random order with equal amounts of energy (3.1 MJ, 741 kcal), fibre and carbohydrates and a 1-week washout period. Meals were a high protein, low fat (30% protein, 51% carbohydrates, 19% fat) meal and a low protein, high fat (15% protein, 51% carbohydrates, 34% fat) meal. Subjects were matched for age and body mass index. Plasma glucose and insulin were measured at fasting, 30, 60, 90, 120 min post-prandially. Insulin resistance and insulin sensitivity were assessed.

RESULTS

There was no significant meal effect on glucose and insulin responses within groups. Glucose response was higher in diabetic (120 min 11 +/- 0.7 mmol L(-1)) compared to nondiabetic (120 min 5 +/- 0.2; P < 0.001) subjects. Diabetic subjects had significantly higher insulin resistance (P < 0.001) and lower insulin sensitivity (P < 0.001) than nondiabetics. Although peak insulin levels, 60 min post-prandially, did not differ between groups (81 +/- 9 pmol L(-1) for diabetic versus 79 +/- 7 pmol L(-1) for nondiabetic subjects), they were achieved much later, 90 min post-prandially, in diabetic, (99 +/- 8 pmol L(-1)) compared to nondiabetic (63 +/- 7 pmol L(-1), P = 0.002) subjects.

CONCLUSIONS

Manipulating protein to fat ratio in meals does not affect post-prandial plasma blood glucose or insulin responses in obese people with and without DM2.

A high mixed protein diet reduces body fat without altering the mechanical properties of bone in female rats

Long-term consumption of high-protein (HP) diets at 35% of energy is postulated to negatively influence bone health. Previous studies have not comprehensively examined the biochemical, physical, and biomechanical properties of bone required to arrive at this conclusion. Our objective in this study was to examine the long-term effect of a HP diet on bone metabolism, mass, and strength in rats. Adult female Sprague-Dawley rats (n = 80) were randomized to receive for 4, 8, 12, or 17 mo a normal-protein (NP) control diet (15% of energy) or a HP diet (35% of energy). Diets were balanced for calcium because the protein sources were rich in calcium. At each time point, measurements included weight, body composition, and bone mass using dual-energy X-ray absorptiometry, mechanical strength at the mid-diaphysis of femur and tibia, microarchitecture of femurs using microcomputerized tomography and serum osteocalcin, carboxy-terminal crosslinks of type I collagen (CTX), insulin-like growth factor-1 (IGF-1), leptin, and adiponectin. Effects of diet, time, and their interaction were tested using factorial ANOVA. The HP diet resulted in lower body weight, total body, and abdominal fat and higher lean mass. Serum leptin and adiponectin were greater in HP-fed than in NP-fed rats, but IGF-1 did not differ between the groups. Whereas the HP diet resulted in higher relative bone mineral content (g/kg) in the femur, tibia, and vertebrae, serum osteocalcin and CTX and bone internal architecture and biomechanical strength were unaffected. In conclusion, HP diets at 35% of energy lower body fat content without hindering the mechanical and weight-bearing properties of bone.

High protein diets decrease total and abdominal fat and improve CVD risk profile in overweight and obese men and women with elevated triacylglycerol

BACKGROUND AND AIMS

It is unclear whether high protein weight loss diets have beneficial effects on weight loss, abdominal fat mass, lipids, glucose and insulin compared to conventional low fat diets in subjects at increased risk of cardiovascular disease (CVD) because of elevated glucose and triglyceride concentrations. Our objective was to determine the effects of high protein (HP) compared to standard protein (SP) diets on CVD risk in obese adults.

METHODS AND RESULTS

Data from three, 12 week, randomized parallel trials with subjects assigned to either HP or SP diet (5500-6500 kJ/day) were pooled. Weight, body composition (dual energy X-ray absorptiometry), lipids, insulin and glucose were measured before and after weight loss. Data from 215 subjects (49.9+/-9.8 years, BMI 33.5+/-3.7 kg/m(2)), 108 HP, 107 SP were analyzed. Weight loss (HP diet 7.82+/-0.37 kg; SP diet 7.65+/-0.39 kg, NS) and total fat loss were not different (HP 6.8+/-4.3 kg; LP 6.4+/-4.7 kg, NS on intention to treat analysis). The reduction in triacylglycerol (TAG) was greater on HP than SP 0.48+/-0.07 mmol/L vs 0.27+/-0.06 mmol/L, (P<0.001). Subjects with TAG greater than the median (>1.54 mmol/L at baseline) lost more weight (HP 8.5+/-0.6; SP 6.9+/-0.6 kg, P=0.01, diet by TG group), total (HP 6.17+/-0.50 kg; SP 4.52+/-0.52 kg, P=0.007) and abdominal fat (HP 1.92+/-0.17 kg; SP 1.23+/-0.19 kg, P=0.005) on HP. Total cholesterol (12 vs 6%, HP vs SP) and TAG (39 vs 20%, HP vs SP) decreased to a greater extent in these subjects (both P</=0.05) on HP.

CONCLUSION

Short-term high protein weight loss diets had beneficial effects on total cholesterol and triacylglycerol in overweight and obese subjects and achieved greater weight loss and better lipid results in subjects at increased risk of CVD. These observations provide further information regarding the utility of this dietary approach in effectively managing body weight and composition and reducing CVD risk in overweight and obese individuals.

Effects of a popular exercise and weight loss program on weight loss, body composition, energy expenditure and health in obese women

OBJECTIVE

To determine the safety and efficacy of altering the ratio of carbohydrate and protein in low-energy diets in conjunction with a popular exercise program in obese women.

DESIGN

Matched, prospective clinical intervention study to assess efficacy of varying ratios of carbohydrate and protein intake in conjunction with a regular exercise program.

PARTICIPANTS

One-hundred sixty one sedentary, obese, pre-menopausal women (38.5 ± 8.5 yrs, 164.2 ± 6.7 cm, 94.2 ± 18.8 kg, 34.9 ± 6.4 kg.m⁻², 43.8 ± 4.2%) participated in this study. Participants were weight stable and not participating in additional weight loss programs.

METHODS

Participants were assigned to either a no exercise + no diet control (CON), a no diet + exercise group (ND), or one of four diet + exercise groups (presented as kcals; % carbohydrate: protein: fat): 1) a high energy, high carbohydrate, low protein diet (HED) [2,600; 55:15:30%], 2) a very low carbohydrate, high protein diet (VLCHP) [1,200 kcals; 63:7:30%], 3) a low carbohydrate, moderate protein diet (LCMP) [1,200 kcals; 50:20:30%] and 4) a high carbohydrate, low protein diet (HCLP) [1,200 kcals; 55:15:30%]. Participants in exercise groups (all but CON) performed a pneumatic resistance-based, circuit training program under supervision three times per week.

MEASUREMENTS

Anthropometric, body composition, resting energy expenditure (REE), fasting blood samples and muscular fitness assessments were examined at baseline and weeks 2, 10 and 14.

RESULTS

All groups except CON experienced significant reductions (P < 0.05 - 0.001) in waist circumference over 14 weeks. VLCHP, LCHP and LPHC participants experienced similar but significant (P < 0.05 - 0.001) reductions in body mass when compared to other groups. Delta responses indicated that fat loss after 14 weeks was significantly greatest in VLCHP (95% CI: -5.2, -3.2 kg), LCMP (-4.0, -1.9 kg) and HCLP (-3.8, -2.1 kg) when compared to other groups. Subsequent reductions in % body fat were significantly greater in VLCHP, LCMP and HCLP participants. Initial dieting decreased (P < 0.05) relative REE similarly in all groups. All exercise groups significantly (P < 0.05) improved in muscular fitness, but these improvements were not different among groups. Favorable but non-significant mean changes occurred in lipid panels, glucose and HOMA-IR. Leptin levels decreased (P < 0.05) in all groups, except for CON, after two weeks of dieting and remained lower throughout the 14 week program. Exercise participation resulted in significant improvements in quality of life and body image.

CONCLUSION

Exercise alone (ND) appears to have minimal impact on measured outcomes with positive outcomes apparent when exercise is combined with a hypoenergetic diet. Greater improvements in waist circumference and body composition occurred when carbohydrate is replaced in the diet with protein. Weight loss in all diet groups (VLCHP, LCMP and HCLP) was primarily fat and stimulated improvements in markers of cardiovascular disease risk, body composition, energy expenditure and psychosocial parameters.