Weight loss maintenance in overweight subjects on ad libitum diets with high or low protein content and glycemic index: the DIOGENES trial 12-month results

Background:A high dietary protein (P) content and low glycemic index (GI) have been suggested to be beneficial for weight management, but long-term studies are scarce.Objective:The DIOGENES randomized clinical trial investigated the effect of P and GI on weight loss maintenance in overweight or obese adults in 8 centers across Europe. This study reports the 1-year results in 2 of the centers that extended the intervention to 1 year.Method:After an 8-week low calorie diet (LCD), 256 adults (BMI>27 kg/m2) were randomized to 5 ad libitum diets for 12 months: high P/low GI (HP/LGI), high P/high GI (HP/HGI), low P/low GI (LP/LGI), low P/high GI (LP/HGI) and a control diet. During the first 6 months foods were provided for free through a shop system, during the whole 12-month period subjects received guidance by a dietician. Primary outcome variable was the change in body weight over the 12-month intervention period.Results:During the LCD period subjects lost 11.2 (10.8, 12.0) kg (mean (95% CI)). Average weight regain over the 12-month intervention period was 3.9 (95% CI 3.0 to 4.8) kg. Subjects on the HP diets regained less weight than subjects on the LP diets. The difference in weight regain after 1 year was 2.0 (0.4, 3.6) kg (P=0.017) (completers analysis, N=139) or 2.8 (1.4, 4.1) kg (P<0.001) (intention-to-treat analysis, N=256). No consistent effect of GI on weight regain was found. There were no clinically relevant differences in changes in cardiometabolic risk factors among diet groups.Conclusion:A higher protein content of an ad libitum diet improves weight loss maintenance in overweight and obese adults over 12 months.International Journal of Obesity accepted article preview online, 28 March 2014; doi:10.1038/ijo.2014.52