New York - Some weight-loss plans shun carbohydrates while others ban fat, but in the new study, researchers found that overweight adults who were instructed to focus on lower-calorie foods lost more weight than their peers who were simply told to cut their overall calories.
The key, according to the study authors, is that foods such as fruits and vegetables have low "energy density". Because they have a high water content, they are heavy by weight but low in calories; while such foods do not add many calories to the diet, they are still filling.
Of the 658 men and women in the current study, those who made the greatest reductions in the energy or calorie density of their diets lost an average of 6kg over 6 months. That compared with 2.2kg in the group that made the smallest reduction in energy density.
Jenny H. Ledikwe, of Pennsylvania State University, and her colleagues report the findings in the American Journal of Clinical Nutrition.
The study included generally healthy men and women with borderline-high blood pressure who were randomly assigned to one of three groups, to look at the effect on blood pressure.
In one group, participants had a single counseling session where they received diet and lifestyle advice intended to lower their blood pressure.
Those in the other two groups attended 18 group meetings and counseling sessions where they set goals for lifestyle changes and weight loss.
The difference was that one group was told to follow the "DASH" diet, which emphasized getting 9 to 12 daily servings of fruits and vegetables, and 2 to 3 servings of low-fat dairy products. The other group was told to reduce their calorie intake, but was not given goals for fruit, vegetable and dairy intake.
Overall, Ledikwe's team found, the DASH group cut down the most on calorie density, even though they actually started eating more food by weight -- a consequence of getting more fruits and vegetables. Those who cut their calorie density the most also shed the most weight.
Diets that emphasize low-calorie foods may be easier to stick to than diets that focus on foods to avoid, the investigators point out, as well as more healthful. In this study, people who cut the calorie density of their diets generally increased their intake of fiber, vitamins and minerals.
"Whereas a decrease in body weight is a primary goal of a weight-loss diet," Ledikwe and her colleagues write, "consideration of nutritional quality is equally important."
SOURCE: American Journal of Clinical Nutrition .
