Diets with high or low protein content and glycemic index for weight-loss maintenance

BACKGROUND: Studies of weight-control diets that are high in protein or low in glycemic index have reached varied conclusions, probably owing to the fact that the studies had insufficient power. METHODS: We enrolled overweight adults from eight European countries who had lost at least 8% of their initial body weight with a 3.3-MJ (800-kcal) low-calorie diet. Participants were randomly assigned, in a two-by-two factorial design, to one of five ad libitum diets to prevent weight regain over a 26-week period: a low-protein and low-glycemic-index diet, a low-protein and high-glycemic-index diet, a high-protein and low-glycemic-index diet, a high-protein and high-glycemic-index diet, or a control diet. RESULTS: A total of 1209 adults were screened (mean age, 41 years; body-mass index [the weight in kilograms divided by the square of the height in meters], 34), of whom 938 entered the low-calorie-diet phase of the study. A total of 773 participants who completed that phase were randomly assigned to one of the five maintenance diets; 548 completed the intervention (71%). Fewer participants in the high-protein and the low-glycemic-index groups than in the low-protein-high-glycemic-index group dropped out of the study (26.4% and 25.6%, respectively, vs. 37.4%; P=0.02 and P=0.01 for the respective comparisons). The mean initial weight loss with the low-calorie diet was 11.0 kg. In the analysis of participants who completed the study, only the low-protein-high-glycemic-index diet was associated with subsequent significant weight regain (1.67 kg; 95% confidence interval [CI], 0.48 to 2.87). In an intention-to-treat analysis, the weight regain was 0.93 kg less (95% CI, 0.31 to 1.55) in the groups assigned to a high-protein diet than in those assigned to a low-protein diet (P=0.003) and 0.95 kg less (95% CI, 0.33 to 1.57) in the groups assigned to a low-glycemic-index diet than in those assigned to a high-glycemic-index diet (P=0.003). The analysis involving participants who completed the intervention produced similar results. The groups did not differ significantly with respect to diet-related adverse events. CONCLUSIONS: In this large European study, a modest increase in protein content and a modest reduction in the glycemic index led to an improvement in study completion and maintenance of weight loss

Higher protein diets consumed ad libitum improve cardiovascular risk markers in children of overweight parents from eight European countries.

Dietary strategies to improve early cardiovascular markers in overweight children are needed. We investigated the effect of dietary protein and glycemic index (GI) on cardiovascular markers and:metabolic syndrome (MetS) scores in 5- to 18-y-old children of overweight/obese parents from 8 European centers. Families were randomized to 1 of 5 diets consumed ad libitum: high protein (HP) or low protein (LP) combined with. high GI (HGI) or low GI (LGI), or a control diet. At 6 centers, families received dietary instruction (instruction centers); at 2 centers, free foods were also provided (supermarket centers). Diet, anthropometry, blood pressure, and serum cardiovascular markers (lipid profile, glucose regulation, and inflammation) were measured in 253 children at baseline, 1 mo, and/or 6 mo. Protein intake was higher in the HP groups (19.9 +/- 1.3% energy) than in the LP groups at 6 mo (16.8 +/- 1.2% energy) (P = 0.001). The GI was 4.0 points lower (95% CI: 2.1, 6.1) in the LGI compared with the HGI groups (P <0.001). In the supermarket centers, the HP and LP groups differed more in protein intake than did the groups in the instruction centers (P = 0.009), indicating better compliance. The HP diets evoked a 2.7-cm (95% CI: 0.9, 5.1) smaller waist circumference and a 0.25-mmol/L (95% CI: 0.09, 0.41) lower serum LDL cholesterol compared with the LP diets at 6 mo (P <0.007). In a separate supermarket center analysis, the HP compared with LP diets reduced waist circumference (P = 0.004), blood pressure. (P <0.01), serum insulin (P = 0.013), and homeostasis model of assessment-insulin resistance (P = 0.016). In the instruction centers, the HP compared with the LP diets reduced LDL cholesterol (P = 0.004). No consistent effect of GI was seen and the MetS scores were not affected. In conclusion increased protein intake improved cardiovascular markers in high-risk children, particularly in those undergoing most intensive intervention