Huge Study Reveals the Secret of Keeping Lost Weight Off
In the past, 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.
Because of this, a team of researchers enrolled overweight adults from eight European countries who had lost at least 8% of their initial body weight with a low-calorie diet. Participants were randomly assigned, in a two-by-two factorial design, to one of five diets to prevent weight regain over a 26-week period. These were: 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.
A total of 1209 adults were screened (mean age, 41 years, 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%).
Significantly 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 (over 24 pounds).
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.
The investigators in this large European study conclude that 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.
Citation: Larsen TM, Dalskov SM, van Baak M, Jebb SA, Papadaki A, Pfeiffer AF, Martinez JA, Handjieva-Darlenska T, Kunešová M, Pihlsgård M, Stender S, Holst C, Saris WH, Astrup A; Diet, Obesity, and Genes (Diogenes) Project. Diet, Obesity, and Genes (Diogenes) Project. Diets with high or low protein content and glycemic index for weight-loss maintenance. New England Journal of Medicine. 2010 Nov 25;363(22): pp.2102-13.