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 x 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. Nutrition and Diabetes (2012) 2, e40; doi:10.1038/nutd.2012.11; published online 13 August 2012