Major Finding: Only subjects assigned to the group with low protein content and high glycemic index showed significant weight regain – a mean of almost 2 kg.
Data Source: A multinational randomized controlled study of five dietary interventions to maintain weight loss for 6 months in 773 obese adults.
Disclosures: This study was funded by the European Commission. Dr. Larsen and his colleagues reported ties to more than 100 food companies and numerous drug companies.
A modest increase in protein content and a modest decrease in glycemic index values allowed study subjects to maintain a 10-kg weight loss better than did other dietary manipulations, according to a randomized trial.
More subjects also were able to continue losing weight while consuming this combination of high-protein, low-glycemic-index foods, said Thomas Meinert Larsen, Ph.D., of the University of Copenhagen and his associates in the Diet, Obesity, and Genes (Diogenes) study.
Diogenes was designed to assess the efficacy of five different maintenance diets in preventing weight regain after obese subjects lost at least 8% of their body weight during an 8-week low-calorie diet. The maintenance diets all contained moderate amounts of fats (25%-30% of total energy consumed), all allowed unrestricted caloric intake, and all attempted to keep alcohol and fiber contents comparable, varying only in their protein content and glycemic indexes.
The study was conducted at research centers throughout Europe. A total of 773 subjects who achieved their target weight loss during the low-calorie-diet period were randomly assigned to continue a 26-week maintenance phase following a diet low in protein (13% of total energy) with a low glycemic index; a diet low in protein with a high glycemic index; a diet high in protein (25% of total energy) with a low glycemic index; a high-protein, high-glycemic index diet; or a control diet with moderate protein content and no guidelines regarding glycemic index (N. Engl. J. Med. 2010;363:2102-13).
The study subjects received dietary counseling every other week for 6 weeks, and then monthly thereafter. They were given recipes, cooking instructions, behavioral advice, and a teaching system to help them achieve the targeted composition of macronutrients.
A total of 29% of the subjects dropped out of the study during this 6-month maintenance phase, a rate nearly 10% higher than expected. Nevertheless, the Diogenes participants “were probably a more adherent group than participants in other studies, since they had adhered sufficiently to the low-calorie diet for 8 weeks to lose at least 8% of their body weight,” Dr. Larsen and his colleagues said, adding that “[d]espite issues of adherence, we believe that our results are generalizable to obese people, particularly if diets are facilitated by easy access to low-glycemic-index foods.”
Weight regain was significantly higher in the low-protein groups and the high-glycemic-index groups. In contrast, both the high-protein and low-glycemic-index groups were more likely to maintain their weight loss and to lose an additional 5% of their body weight.
Only subjects assigned to the group with low protein content and high glycemic index showed significant weight regain – a mean of almost 2 kg.
These findings show that “even a modest increase in dietary protein or a modest reduction in glycemic-index values was sufficient to minimize weight regain and promote further weight loss in obese patients after a successful weight-loss diet,” they said.
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More Time Will Tell
The main limitation of this study was the relatively short duration of follow-up.
“A 2-kg difference in body weight, by itself, has limited practical implications.
“But a diet that could effectively prevent weight regain over the long term would have major public health significance. In this regard, the 12-month and longer follow-up data will be informative,” Dr. David S. Ludwig and Cara B. Ebbeling, Ph.D., noted.
DR. LUDWIG and DR. EBBELING are with the Optimal Weight for Life Program at Children's Hospital and in the pediatrics department at Harvard University, Boston. These comments were taken from an editorial accompanying Dr. Larsen's report (N. Engl. J. Med. 2010;363:2159-61).