Thanksgiving is not a day for counting calories. But for people who have dieted this year and are trying to maintain a healthful weight, turkey leftovers — without the stuffing — may be a smart strategy going forward, according to a new report.
In the largest diet study in Europe to date, foods that were high in protein and low on the glycemic index — such as poultry, eggs, fish and nuts — did the best job of helping people maintain their weight loss for 26 weeks, researchers report in Thursday's edition of the New England Journal of Medicine.
The diet also was the easiest for study participants to adhere to among the five weight-maintenance diets tested, the study found.
Though many people can lose weight, "maintaining weight loss is the difficult part," said study leader Thomas Meinert Larsen, an associate professor of food composition and obesity at the University of Copenhagen. "You have to come up with a diet that is easy to follow and is practical long-term. It's reassuring that the most effective diet in our study seems to be the one that is best maintained."
Larsen and his colleagues from around Europe assigned 773 adults who had already lost an average of about 24 pounds to one of five healthful diets designed to encourage a stable weight. All of the diets had a moderate fat content — 25% to 30% of calories from fat — were low on sugar, high in fiber and had no limits on calories consumed daily. However, the participants were asked to watch their portion sizes and adhere to strict criteria, which varied among the groups, regarding the amount of protein consumed and glycemic index.
Glycemic index is a measure of how quickly carbohydrates in food break down and affect blood sugar levels. Those that do so swiftly are assigned a value of 70 or above, while those that break down more slowly and release glucose gradually typically have a value below 55. The glycemic index of white bread is 70, for example, whereas chicken is about 45.
To make sure they followed their diets, the study participants were counseled on what foods to prepare, submitted food diaries and underwent urine tests to check the amount of protein they consumed. A small portion of the participants had their meals prepared for them.
After 26 weeks, those who followed the high-protein, low-glycemic-index diet lost an average of 0.8 pounds. Participants in the other groups gained an average of 0.7 to 3.7 pounds, according to the study. Overall, volunteers who followed a low-protein diet gained an average of 2 pounds more than those who followed a high-protein diet, and those who ate high-glycemic-index foods gained 2 pounds more, on average, than those who ate low-glycemic-index foods.
In addition, those in the high-protein, low-glycemic-index group had the lowest dropout rate — about 26%, compared with an average of 37% for the other groups, the researchers reported.
The study suggests that people feel more satisfied on the high-protein, low-glycemic-index diet and thus will stick with it longer, said Dr. David Ludwig, director of the Optimal Weight for Life program at Children's Hospital Boston and coauthor of an editorial accompanying the study.
Ludwig also noted that the diets followed by the five groups differed only modestly. The glycemic index varied by five units between the highest and lowest groups, and the proportion of calories obtained from protein varied by a mere 5%.
"A more powerful intervention supported by additional food products might produce an even greater effect, although ultimately we need longer-term research," he said.
James O. Hill, director of the Center for Human Nutrition at the University of Colorado, agreed that longer-term data would be more convincing. "There is not much difference among the groups right now," said Hill, who wasn't involved with the study.
Still, he praised the researchers for focusing on weight maintenance, an often-overlooked aspect of weight loss that requires a different approach than for the initial shedding of pounds.
"This is the kind of research that ought to be done," he said.
Nutrition researchers have not reached a consensus about how much protein and glycemic index matter for weight loss and weight control. High-protein diets, however, have been shown to be successful in the active phase of weight loss, along with many other types of diets.
Researchers have also examined the children of those participating in the study. Among kids whose families prepared high-protein, low-glycemic-index foods, the proportion who were overweight dropped from 46% at the start of the study to 39% half a year later. Those results were published this month in the journal Pediatrics.