Context: Incidence of insulin resistance (IR) in Americans is steadily rising. IR may be ameliorated with < or = 5% loss in body weight.
Objective: To examine effects of 2 weight-loss diets on body weight and composition in overweight adults with IR.
Design: Participants randomly assigned to a high-protein, low-fat (HPLF) or a high-carbohydrate, low-fat (HCLF) diet for 8 weeks.
Setting: All meals prepared and weighed in the metabolic kitchen at Arizona State University. Lunch consumed on-site; all other meals packaged for home consumption.
Patients: Twenty overweight, healthy participants with elevated fasting serum insulin (> or = 15 microU/L) were recruited.
Interventions: 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.
Main outcome measures: Body composition, etabolic indices, fasting plasma glucose, and insulin.
Results: 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).
Conclusion: Both diets promoted > or = 5% loss in body weight and significantly reduced percent body fat.