Effects of an 8-week high-protein or high-carbohydrate diet in adults with hyperinsulinemia.

Incidence of insulin resistance (IR) in Americans is steadily rising. IR may be ameliorated with < or = 5% loss in body weight. To examine effects of 2 weight-loss diets on body weight and composition in overweight adults with IR. Participants randomly assigned to a high-protein, low-fat (HPLF) or a high-carbohydrate, low-fat (HCLF) diet for 8 weeks. All meals prepared and weighed in the metabolic kitchen at Arizona State University. Lunch consumed on-site; all other meals packaged for home consumption. Twenty overweight, healthy participants with elevated fasting serum insulin (> or = 15 microU/L) were recruited. Both diets were low-fat (27% kcal from fat; < 7% saturated, < or = 10% monounsaturated, and < or = 10% polyunsaturated) and energy-restricted (energy levels were 1200, 1500, 1700 or 2000 kcal); HPLF: 32% protein, 41% carbohydrate; HCLF: 59% carbohydrate, 14% protein. Energy levels were assigned on the basis of participant's resting metabolic rate. Body composition, etabolic indices, fasting plasma glucose, and insulin. No significant differences were found in the main outcome measures between the diets. Body weight (HPLF: -4.9 kg; HCLF: -4.0 kg) and total percent body fat (HPLF: -1.5%; HCLF: -0.4%) significantly reduced from baseline to week 8 (P = .005 and P = .035, respectively). Both diets promoted > or = 5% loss in body weight and significantly reduced percent body fat.