Nov. 7, 2008 -- As any so-called yo-yo dieter can tell you, it is often easier to lose weight than to keep it off. A new study shows that different diet compositions -- such as more fat or less fat, higher or lower glycemic index, and different levels of monounsaturated fatty acids -- don't affect a dieter's tendency to regain the weight.
First, they were put on a hard-core diet, consisting mostly of shakes and bars, for eight weeks. Those who lost at least 8% of their body weight were then asked to participate in the rest of the study, which focused on weight maintenance.
Each participant went on one of three maintenance diets. Food was provided free of charge at a market built for the study. The diets were:
- New healthy pyramid diet, consisting of moderate amounts of fat (35%-45% of calories) and high amounts (more than 20% of calories) of monounsaturated fatty acids such as olive oil. This diet also calls for fewer carbohydrates that have a high glycemic index, such as refined breads and pasta.
- USDA Pyramid, which includes a low amount of fat (20%-30% of calories) and a moderate glycemic index.
- Control group, designed to mimic a typical Western diet, with 35% of calories as fat, a high amount of saturated fatty acids, and a high glycemic index.
In all three diets, protein accounted for 10%-20% of calories.
Across the board, dieters regained weight, but 60% maintained at least 10% weight loss from one to five years.
There were some discrepancies in other measures -- the new healthy eating pyramid diet seemed to have a positive impact on diabetes risk factors, for instance. However, these positives would likely disappear if participants continued to gain weight.
It takes more than dietary changes to sustain weight loss long term; the frequency of exercise was considered the strongest predictor of weight loss maintenance. Current guidelines recommend 60 minutes daily of moderate physical activity.
"We need to look further than diet composition and other factors such as physical activity, and eating behavior needs to be taken into consideration for the prevention of obesity," the authors conclude in the study, which was published in the American Journal of Clinical Nutrition.
In an accompanying editorial, authors suggest that weight loss strategies should be individualized and geared toward improving healthy parameters and the prevention of weight gain, with less emphasis on initial weight loss. Diets low in refined carbs, avoiding trans fats from hydrogenated oils, and moderate intake of unsaturated fats are recommended because of the health benefits -- despite only moderate weight loss.