Changes in renal function during weight loss induced by high vs low-protein low-fat diets in overweight subjects

BACKGROUND: Due to the high satiating effect of protein, a high-protein die t may be desirable in the treatment of obesity, However the long-term effec t of different levels of protein intake on renal function is unclear. OBJECTIVE: To assess the renal effects of high vs low protein contents in f at-reduced diets. DESIGN: Randomized 6 months dietary intervention study comparing two contro lled ad libitum diets with 30 energy (E%) fat content: high-protein (HP; 25 E%) or low-protein, (LP, 12 E% protein), All food was provided by self-sel ection in a shop at the department, and high compliance to the diet composi tion was confirmed by measurements of urinary nitrogen excretion. SUBJECTS: 65 healthy, overweight and obese (25 < body mass index (BMI) < 34 kg/m(2)). RESULTS: Dietary protein intake changed from 91.1 gld to a 6 months interve ntion average of 70.4 g/d (P < 0.05) in the LP group and from 91.4 g/d to 1 07.8 g/d (P < 0.05) in the HP group, producing changes in glomular filtrati on rate (GFR) of - 7.1 ml/min in the LP group and + 5.2 ml/min in the HP gr oup (group effect: P < 0.05). Kidney volume decreased by - 6.2 cm(3) in the HP group and increased by + 9.1 cm(3) in the HP group (P < 0.05), whereas albuminuria remained unchanged in all groups. CONCLUSION: Moderate changes in dietary protein intake cause adaptive alter ations in renal size and function without indications of adverse effects.