Diets with High or Low Protein Content and Glycemic Index for Weight-Loss Maintenance

original article
The new england journal o f medicine
n engl j med 363;22 nejm.org 2102 november 25, 2010


Diets with High or Low Protein Content and
Glycemic Index for Weight-Loss Maintenance


N Engl J Med 2010;363:2102-13.
Copyright © 2010 Massachusetts Medical Society.
Abstract
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-glycemicindex
diet, a low-protein and high-glycemic-index diet, a high-protein and lowglycemic-
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 lowglycemic-
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 lowprotein–
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. (Funded by the European Commission; ClinicalTrials.gov
number, NCT00390637.)
n engl j med 363;22 nejm.org 2102 november 25, 2010
The New England Journal of Medicine


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