Manny Noakes

Energy Restriction and Weight Loss on Very-Low-Fat Diets Reduce C-Reactive Protein Concentrations in Obese, Healthy Women

C-reactive protein (CRP) is an inflammatory-response protein that is a strong, independent predictor of cardiovascular mortality. CRP is positively associated with body mass index (BMI). In this study, we investigated the effects of dynamic weight loss on CRP in 83 healthy, obese women (mean BMI, 33.8±0.4 kg/m2; range, 28.2 to 43.8 kg/m2). Subjects were placed on very-low-fat, energy-restricted diets (5700 kJ, 15% fat) for 12 weeks. Weight, waist and hip circumferences, plasma lipids, glucose, and CRP were measured at baseline and after 12 weeks. CRP was positively associated with BMI (r =0.281, P =0.01) and waist circumference (r =0.278, P =0.01) but was not related to other atherosclerosis risk factors. BMI was significantly different between groups split above or below the median for CRP (34.8±0.6 kg/m2 vs 33.0±0.5 kg/m2, P =0.02). After 12 weeks, weight loss was 7.9±0.3 kg. CRP was significantly decreased by 26% (P < 0.001), and a correlation was observed between weight loss and the change in CRP (r =0.309, P =0.005). The variance in the change in CRP was partly explained by initial CRP (13.6%), energy intake (5.4%), and percentage weight loss (4.6%, P =0.001). This study confirms recent observations that BMI is associated with CRP, a marker for low-grade systemic inflammation. Furthermore, we observed that CRP was lowered in proportion to weight loss.

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.

Long-term effects of a high-protein, low-carbohydrate diet on weight control and cardiovascular risk markers in obese hyperinsulinemic subjects.

OBJECTIVE: To compare the long-term compliance and effects of two low-fat diets differing in carbohydrate to protein ratio on body composition and biomarkers of cardiovascular disease risk in obese subjects with hyperinsulinemia.DESIGN: Outpatient, parallel, clinical intervention study of two groups of subjects randomly assigned to either a standard protein (SP; 15% protein, 55% carbohydrate) or high-protein (HP; 30% protein, 40% carbohydrate) diet, during 12 weeks of energy restriction (∼6.5 MJ/day) and 4 weeks of energy balance (∼8.3 MJ/day). Subsequently, subjects were asked to maintain the same dietary pattern for the succeeding 52 weeks with minimal professional support.SUBJECTS: A total of 58 obese, nondietetic subjects with hyperinsulinemia (13 males/45 females, mean age 50.2 y, mean body mass index (BMI) 34.0 kg/m2, mean fasting insulin 17.8 mU/l) participated in the study.MEASUREMENTS: Body composition, blood pressure, blood lipids, fasting glucose, insulin, CRP and sICAM-1 were measured at baseline and at weeks 16 and 68. Urinary urea/creatinine ratio was measured at baseline, week 16 and at 3 monthly intervals thereafter.RESULTS: In total, 43 subjects completed the study with similar dropouts in each group (P=0.76). At week 68, there was net weight loss (SP −2.9±3.6%, HP −4.1±5.8%; P<0.01) due entirely to fat loss (P<0.001) with no diet effect. Both diets significantly increased HDL cholesterol concentrations (P<0.001) and decreased fasting insulin, insulin resistance, sICAM-1 and CRP levels (P<0.05). Protein intake was significantly greater in HP during the initial 16 weeks (P<0.001), but decreased in HP and increased in SP during 52-week follow-up, with no difference between groups at week 68, indicating poor long-term dietary adherence behaviour to both dietary patterns.CONCLUSION: Without active ongoing dietary advice, adherence to dietary intervention is poor. Nonetheless, both dietary patterns achieved net weight loss and improvements in cardiovascular risk factors.

Cholesterol-lowering effects of plant sterol esters differ in milk, yoghurt, bread and cereal.

Objective: To measure the relative effects of each of four phytosterol ester-enriched low-fat foods (bread, breakfast cereal, milk and yoghurt) on serum lipids, plasma phytosterols and carotenoids.Design: Three research centres undertook a randomised, incomplete crossover, single-blind study consisting of four treatment periods of 3 weeks each, one of which was a control period. Each sterol-enriched test food provided 1.6 g/day of phytosterols as sterol esters.Setting: General Community.Subjects: In all 58, free-living men and women with mean age (s.d.) 54 (8) y, moderately elevated plasma total cholesterol 6.2 (0.7) mmol/l and body mass index 26.2 (3.0) kg/m2.Main outcome measures: Serum lipids, plasma phytosterols and carotenoids.Results: Serum total and LDL cholesterol levels were significantly lowered by consumption of phytosterol-enriched foods: milk (8.7 and 15.9%) and yoghurt (5.6 and 8.6%). Serum LDL cholesterol levels fell significantly by 6.5% with bread and 5.4% with cereal. They were both significantly less efficacious than sterol-enriched milk (P<0.001). Plasma sitosterol increased by 17–23% and campesterol by 48–52% with phytosterol-enriched milk and bread. Lipid-adjusted β-carotene was lowered by 5–10% by sterols in bread and milk, respectively.Conclusions: This is the first study to demonstrate that cholesterol-lowering effects of plant sterol esters may differ according to the food matrix. Plant sterols in low-fat milk was almost three times more effective than in bread and cereal. Despite phytosterol-enriched cereal products resulting in lower serum cholesterol reductions compared to sterol-enriched milk, the detection of similar changes in plasma phytosterols demonstrated that such products still delivered and released phytosterols to the gut.

Long-term effects of a very-low-carbohydrate weight loss diet compared with an isocaloric low-fat diet after 12 mo

BACKGROUND Long-term weight loss and cardiometabolic effects of a very-low-carbohydrate, high-saturated-fat diet (LC) and a high-carbohydrate, low-fat diet (LF) have not been evaluated under isocaloric conditions. OBJECTIVE The objective was to compare an energy-controlled LC diet with an LF diet at 1 y. DESIGN Men and women (n = 118) with abdominal obesity and at least one additional metabolic syndrome risk factor were randomly assigned to either an energy-restricted (approximately 6-7 MJ) LC diet (4%, 35%, and 61% of energy as carbohydrate, protein, and fat, respectively) or an isocaloric LF diet (46%, 24%, and 30% of energy as carbohydrate, protein, and fat, respectively) for 1 y. Weight, body composition, and cardiometabolic risk markers were assessed. RESULTS Sixty-nine participants (59%) completed the trial: 33 in the LC group and 36 in the LF group. Both groups lost similar amounts of weight (LC: -14.5 +/- 1.7 kg; LF: -11.5 +/- 1.2 kg; P = 0.14, time x diet) and body fat (LC: -11.3 +/- 1.5 kg; LF: -9.4 +/- 1.2 kg; P = 0.30). Blood pressure, fasting glucose, insulin, insulin resistance, and C-reactive protein decreased independently of diet composition. Compared with the LF group, the LC group had greater decreases in triglycerides (-0.36 +/- 0.15 mmol/L; 95% CI: -0.67, -0.05 mmol/L; P = 0.011), increases in HDL cholesterol (0.23 +/- 0.09 mmol/L; 95% CI: 0.06, 0.40 mmol/L; P = 0.018) and LDL cholesterol (0.6 +/- 0.2 mmol/L; 95% CI: 0.2, 1.0 mmol/L; P = 0.001), and a greater but nonsignificant increase in apolipoprotein B (0.08 +/- 0.04 g/L; 95% CI: -0.004, 0.171 g/L; P = 0.17). CONCLUSIONS Under planned isoenergetic conditions, as expected, both dietary patterns resulted in similar weight loss and changes in body composition. The LC diet may offer clinical benefits to obese persons with insulin resistance. However, the increase in LDL cholesterol with the LC diet suggests that this measure should be monitored. This trial was registered with the Australian New Zealand Clinical Trials Registry at (http://www.anzctr.org.au) as ACTR 12606000203550.

Diets high and low in glycemic index versus high monounsaturated fat diets: effects on glucose and lipid metabolism in NIDDM

Objective: To examine the relative effects of high and low glycemic index (GI) carbohydrates, and mono-unsaturated fats on blood glucose and lipid metabolism in NIDDM subjects.Subjects: Fourteen male and seven female variably controlled NIDDM subjects recruited by advertisement.Setting: Free living outpatients.Research design: A repeated measures, within-subject design was used such that each subject consumed three diets: (a) a high-GI diet (53% CHO −21% fat, 63 GI units (glucose=100)); (b) a low-GI diet (51% CHO −23% fat, 43 GI units); and (c) a high-mono high-GI diet (42% CHO−35% fat, 59 GI units) in random order and cross-over fashion for four weeks. Approximately 45% energy was provided as key foods which differed in published GI values and specifically excluded legumes. Dietary fibre intake was >30 g/d on each diet. At the end of each dietary intervention, we measured fasting plasma lipids, glucose, insulin, total glycated plasma protein, fructosamine, LDL and HDL particle size as well as 24 h urinary excretion of glucose and C-peptide.Results: HDL-cholesterol was higher on the low-GI and high-mono high-GI diets compared to the high-GI diet (P<0.05 for overall diet effect). There were no other significant differences in metabolic control between diets, even when adjusted for BMI, glucose control or gender. Body weight and saturated fat intake remained stable between dietary interventions.Conclusion: High-mono high-GI and high-CHO, low-GI diets are superior to high-CHO, high-GI diets with respect to HDL metabolism but no effect was noted on glucose metabolism in variably controlled NIDDM subjects.Sponsorship: This study was funded by CSIRO Human Nutrition.

The Effect of a Hypocaloric Diet with and without Exercise Training on Body Composition, Cardiometabolic Risk Profile, and Reproductive Function in Overweight and Obese Women with Polycystic Ovary Syndrome

CONTEXT In overweight women with polycystic ovary syndrome (PCOS), the benefits of the addition of exercise to an energy-restricted diet in further improving cardiometabolic risk factors and reproductive function has not been extensively studied. OBJECTIVE The objective was to evaluate the effects of aerobic and aerobic-resistance exercise when combined with an energy-restricted high protein diet (5000-6000 kJ/d) on metabolic risk factors and reproductive function in women with PCOS. DESIGN AND SETTING A 20-wk outpatient, randomized, parallel study was conducted in a metropolitan research clinic. PATIENTS AND INTERVENTION Ninety-four overweight and obese women with PCOS (age 29.3 +/- 0.7 yr; body mass index 36.1 +/- 0.5 kg/m2) were randomized to diet only (DO; n = 30), diet and aerobic exercise (DA; n = 31), or diet and combined aerobic-resistance exercise (DC; n = 33). MAIN OUTCOME MEASURES Weight, body composition, cardiometabolic risk factors, hormonal status, menstrual cyclicity, and ovulatory function were assessed. RESULTS All interventions reduced weight (DO 8.9 +/- 1.6%, DA 10.6 +/- 1.7%, and DC 8.7 +/- 1.7%; P < 0.001) with no difference between treatments (P = 0.7, time x treatment). Fat mass decreased more (3 kg) and fat-free mass decreased less (2 kg) in DA and DC compared with DO (P < or = 0.03). Reductions in blood pressure (5.6/2.7 mm Hg), triglycerides (0.4 mmol/liter), total cholesterol (0.5 mmol/liter), low-density lipoprotein cholesterol (0.1 mmol/liter), glucose (0.2 mmol/liter), fasting insulin (4.3 mIU/liter), testosterone (0.4 nmol/liter), and free androgen index (2.8) (P < 0.001) and improvements in SHBG (7.0 nmol/liter) and reproductive function occurred in all groups, with no difference between treatments. CONCLUSION In overweight and obese women with PCOS, the addition of aerobic or combined aerobic-resistance exercise to an energy-restricted diet improved body composition but had no additional effect on improvements in cardiometabolic, hormonal, and reproductive outcomes relative to diet alone.

Comparison of Three Bioelectrical Impedance Methods with DXA in Overweight and Obese Men

Objective: To compare bioelectrical impedance analysis (BIA) of body composition using three different methods against DXA in overweight and obese men.

Flow-Mediated Dilatation Is Impaired by a High–Saturated Fat Diet but Not by a High-Carbohydrate Diet

Objective—It is unknown whether a low-fat diet, which may elevate triglycerides and lower high-density lipoprotein (HDL) cholesterol, harms the endothelium. Our aim was to determine whether a low-fat, high-carbohydrate (CARB) diet impaired endothelial vasodilation compared with high saturated fat (SFA), monounsaturated fat (MUFA), or polyunsaturated fat (PUFA) diets. Methods and Results—Forty healthy subjects were randomly crossed over to 4, 3-week isocaloric diets high in PUFA, MUFA, or SFA, containing at least 25 g of the relevant fat or a low-fat, CARB, high–glycemic load diet. Flow-mediated dilatation (FMD), fasting blood lipids, high sensitivity C-reactive protein, plasma intercellular, and vascular adhesion molecules plasma E- and P-selectin were measured after each intervention. SFA impaired FMD compared with all other diets (5.41±2.45% versus 10.80±3.69%; P=0.01). FMD did not change on CARB relative to MUFA or PUFA, despite 23% to 39% rises in triglyceride and 10% to 15% falls in HDL cholesterol. P-selectin was highest after SFA (121±52.7 ng/mL) versus MUFA (98±44.5 ng/mL; P=0.001) and PUFA (96±36.4 ng/mL; P=0.001). Conclusion—High SFA caused deterioration in FMD compared with high PUFA, MUFA, or CARB diets. Inflammatory responses may also be increased on this diet.

Comparative effects of very low-carbohydrate, high-fat and high-carbohydrate, low-fat weight-loss diets on bowel habit and faecal short-chain fatty acids and bacterial populations

Very low-carbohydrate diets are often used to promote weight loss, but their effects on bowel health and function are largely unknown. We compared the effects of a very low-carbohydrate, high-fat (LC) diet with a high-carbohydrate, high-fibre, low-fat (HC) diet on indices of bowel health and function. In a parallel study design, ninety-one overweight and obese participants (age 50.6 (sd 7.5) years; BMI 33.7 (sd 4.2) kg/m(2)) were randomly assigned to either an energy-restricted (about 6-7 MJ, 30 % deficit) planned isoenergetic LC or HC diet for 8 weeks. At baseline and week 8, 24 h urine and faecal collections were obtained and a bowel function questionnaire was completed. Compared with the HC group, there were significant reductions in the LC group for faecal output (21 (sd 145) v. - 61 (sd 147) g), defecation frequency, faecal excretion and concentrations of butyrate ( - 0.5 (sd 10.4) v. - 3.9 (sd 9.7) mmol/l) and total SCFA (1.4 (sd 40.5) v. - 15.8 (sd 43.6) mmol/l) and counts of bifidobacteria (P < 0.05 time x diet interaction, for all). Urinary phenols and p-cresol excretion decreased (P < or = 0.003 for time) with no difference between diets (P > or = 0.25). Faecal form, pH, ammonia concentration and numbers of coliforms and Escherichia coli did not change with either diet. No differences between the diets were evident for incidences of adverse gastrointestinal symptoms, which suggests that both diets were well tolerated. Under energy-restricted conditions, a short-term LC diet lowered stool weight and had detrimental effects on the concentration and excretion of faecal SCFA compared with an HC diet. This suggests that the long-term consumption of an LC diet may increase the risk of development of gastrointestinal disorders.