Thomas P. Wycherley

Effects of energy-restricted high-protein, low-fat compared with standard-protein, low-fat diets: a meta-analysis of randomized controlled trials

BACKGROUND It is currently unclear whether altering the carbohydrate-to-protein ratio of low-fat, energy-restricted diets augments weight loss and cardiometabolic risk markers. OBJECTIVE The objective was to conduct a systematic review and meta-analysis of studies that compared energy-restricted, isocaloric, high-protein, low-fat (HP) diets with standard-protein, low-fat (SP) diets on weight loss, body composition, resting energy expenditure (REE), satiety and appetite, and cardiometabolic risk factors. DESIGN Systematic searches were conducted by using MEDLINE, EMBASE, PubMed, and the Cochrane Central Register of Controlled Trials to identify weight-loss trials that compared isocalorically prescribed diets matched for fat intake but that differed in protein and carbohydrate intakes in participants aged ≥18 y. Twenty-four trials that included 1063 individuals satisfied the inclusion criteria. RESULTS Mean (±SD) diet duration was 12.1 ± 9.3 wk. Compared with an SP diet, an HP diet produced more favorable changes in weighted mean differences for reductions in body weight (-0.79 kg; 95% CI: -1.50, -0.08 kg), fat mass (FM; -0.87 kg; 95% CI: -1.26, -0.48 kg), and triglycerides (-0.23 mmol/L; 95% CI: -0.33, -0.12 mmol/L) and mitigation of reductions in fat-free mass (FFM; 0.43 kg; 95% CI: 0.09, 0.78 kg) and REE (595.5 kJ/d; 95% CI: 67.0, 1124.1 kJ/d). Changes in fasting plasma glucose, fasting insulin, blood pressure, and total, LDL, and HDL cholesterol were similar across dietary treatments (P ≥ 0.20). Greater satiety with HP was reported in 3 of 5 studies. CONCLUSION Compared with an energy-restricted SP diet, an isocalorically prescribed HP diet provides modest benefits for reductions in body weight, FM, and triglycerides and for mitigating reductions in FFM and REE.

A High Protein Diet With Resistance Exercise Training Improves Weight Loss And Body Composition In Overweight And Obese Patients With Type 2 Diabetes

OBJECTIVE To evaluate the effects of two low-fat hypocaloric diets differing in the carbohydrate-to-protein ratio, with and without resistance exercise training (RT), on weight loss, body composition, and cardiovascular disease (CVD) risk outcomes in overweight/obese patients with type 2 diabetes. RESEARCH DESIGN AND METHODS A total of 83 men and women with type 2 diabetes (aged 56.1 ± 7.5 years, BMI 35.4 ± 4.6 kg/m2) were randomly assigned to an isocaloric, energy-restricted diet (female subjects 6 MJ/day, male subjects 7 MJ/day) of either standard carbohydrate (CON; carbohydrate:protein:fat 53:19:26) or high protein (HP; 43:33:22), with or without supervised RT (3 days/week) for 16 weeks. Body weight and composition, waist circumference (WC), and cardiometabolic risk markers were assessed. RESULTS Fifty-nine participants completed the study. There was a significant group effect (P ≤ 0.04) for body weight, fat mass, and WC with the greatest reductions occuring in HP+RT (weight [CON: −8.6 ± 4.6 kg, HP: −9.0 ± 4.8 kg, CON+RT: −10.5 ± 5.1 kg, HP+RT: −13.8 ± 6.0 kg], fat mass [CON: −6.4 ± 3.4 kg, HP: −6.7 ± 4.0 kg, CON+RT: −7.9 ± 3.7 kg, HP+RT: −11.1 ± 3.7 kg], and WC [CON: −8.2 ± 4.6 cm, HP: −8.9 ± 3.9 cm, CON+RT: −11.3 ± 4.6 cm, HP+RT: −13.7 ± 4.6 cm]). There was an overall reduction (P < 0.001) in fat-free mass (−2.0 ± 2.3 kg), blood pressure (−15/8 ± 10/6 mmHg), glucose (−2.1 ± 2.2 mmol/l), insulin (−4.7 ± 5.4 mU/l), A1C (−1.25 ± 0.94%), triglycerides (−0.47 ± 0.81 mmol/l), total cholesterol (−0.67 ± 0.69 mmol/l), and LDL cholesterol (−0.37 ± 0.53 mmol/l), with no difference between groups (P ≥ 0.17). CONCLUSIONS An energy-restricted HP diet combined with RT achieved greater weight loss and more favorable changes in body composition. All treatments had similar improvements in glycemic control and CVD risk markers.

Long-term effects of weight loss with a very low carbohydrate and low fat diet on vascular function in overweight and obese patients

Abstract.  Wycherley TP, Brinkworth GD, Keogh JB, Noakes M, Buckley JD, Clifton PM. (Commonwealth Scientific and Industrial Research Organization, Food and Nutritional Sciences; School of Molecular and Biomedical Science, University of Adelaide; and Nutritional Physiology Research Centre and Australian Technology Network Centre for Metabolic Fitness, Sansom Institute for Health Research, University of South Australia). Long‐term effects of weight loss with a very low carbohydrate and low fat diet on vascular function in overweight and obese patients. J Intern Med 2010; 267: 452–461.

Effect of caloric restriction with and without exercise training on oxidative stress and endothelial function in obese subjects with type 2 diabetes.

Aim:  Effects of dietary weight loss on endothelial function, particularly when combined with exercise training, is largely unknown in type 2 diabetes. We sought to determine whether aerobic exercise training provided any additional improvements in endothelial function, oxidative stress or other established markers of cardiovascular risk when combined with an energy‐restricted diet in patients with type 2 diabetes.

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.

Moderate weight loss improves heart rate variability in overweight and obese adults with type 2 diabetes

The objective of this study was to determine the effects of weight loss on heart rate variability (HRV) and its association with traditional cardiovascular disease risk factors in overweight and obese patients with type 2 diabetes. Forty five patients [body mass index (BMI) 35.4 ± 0.7 kg/m²; age 56.5 ± 1.1 yr] with type 2 diabetes followed an energy-restricted diet (6-7 MJ/day) for 16 wk. Body weight, blood pressure, glucose, insulin, insulin resistance [homeostasis model assessment index 2 (HOMA2)], glycosylated hemoglobin (HbA1c), total cholesterol, low-density lipoproteins (LDL), high-density lipoproteins (HDL), triglycerides, resting HR, and HRV were measured before and after the intervention period. Mean reduction in body weight was 11.1 ± 1.0 kg (10%), with significant reductions in blood pressure (-10%), total cholesterol (-15.9%), LDL (-17.7%), HDL (-7.5%), triglycerides (-21.2%), glucose (-23.4%), insulin (-37.6%), HOMA2 (-40.1%), and HbA1c (-14.5%) (P ≤ 0.05 for all variables). There were increases in several HRV components, including total power (1,370 ± 280 to 2,045 ± 280 ms²), low-frequency power (345 ± 70 to 600 ± 108 ms²), SD of normal to normal intervals (SDNN; 35.0 ± 2.5 to 43.0 ± 2.7 s), and square root of the mean squared differences of successive normal to normal intervals (RMSSD; 23.0 ± 3.5 to 32.0 ± 3.1 s), and a decrease in HR (69.0 ± 1.3 to 60.0 ± 1.2 beats/min) (P ≤ 0.03 for all variables). Changes in HR, SDNN, total power, and low-frequency power correlated with change in BMI (P < 0.05). In addition to improvements in traditional cardiovascular and metabolic risk factors, weight loss improves HRV in overweight and obese patients with type 2 diabetes.

Self‐reported facilitators of, and impediments to maintenance of healthy lifestyle behaviours following a supervised research‐based lifestyle intervention programme in patients with type 2 diabetes

Diabet. Med. 29, 632–639 (2012)

Reductions in Blood Pressure Following Energy Restriction for Weight Loss Do Not Rebound after Re-Establishment of Energy Balance in Overweight and Obese Subjects

Objective. The objective of the present study was to elucidate the separate effects of energy restriction and weight loss on blood pressure (BP) and to assess the relationship between sodium intake, weight loss, and BP. Methods. Two hundred and eight overweight and obese subjects (age: 52.4   ±   0.8 yrs; BMI 33.6   ±   0.3 kg/m2) completed a weight loss diet program consisting of 8–12 weeks of moderate energy restriction (ER; ∼30% energy deficit, unrestricted salt intake) and four weeks of energy balance (EB). Body weight and BP were measured at baseline, the midpoint, and the end of ER and after EB. 24-hr Na+ excretion was measured at baseline and at the end of EB. Results. Overall, body weight reduced progressively by 7.0   ±   0.2 kg (7.5%; p < 0.001) with the hypocaloric diet. BP fell substantially during the first phase of ER (−5.7   ±   0.7/−2.6   ±   0.4 mmHg, p   =   0.001), corresponding to a 4.5   ±   0.2 kg weight reduction, with no further BP changes during the second phase of ER, despite further weight loss (2.4   ±   0.1 kg). During EB, BP remained stable. The hypotensive effects of caloric restriction and weight loss were similar across clinical subgroups defined by age, sex, diabetes, insulin sensitivity, and hypertensive status. BP responses to weight loss were independent of 24-hr urinary Na+ excretion. 24-hr urinary Na+ excretion was similar at baseline and at the end of EB (146.5   ±   5.3 vs. 146.9   ±   5.3 mmol/24-hr). Conclusion. The hypotensive effects of caloric restriction do not rebound upon return to eucaloric intake at a reduced body weight, and a high sodium intake does not appear to alter the hypotensive effects of weight loss. This reinforces the clinical importance of weight loss and supports the recommendation that strategies for promoting long-term weight loss should become the primary focus of dietary efforts to control BP in overweight patients.

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.

Timing of protein ingestion relative to resistance exercise training does not influence body composition, energy expenditure, glycaemic control or cardiometabolic risk factors in a hypocaloric, high protein diet in patients with type 2 diabetes.

Aim: To investigate timing of protein ingestion relative to resistance exercise training (RT) on body composition, cardiometabolic risk factors, glycaemic control and resting energy expenditure (REE) during weight loss on a high‐protein (HP) diet in overweight and obese patients with type 2 diabetes (T2DM).