The "quality" of calories consumed—not just the quantity—matters when trying to keep off weight without having adverse effects on your body, according to a study of three common diets recently published in JAMA.
Previous research has shown that weight loss lowers daily energy expenditure, likely making it easier for dieters to regain weight. As such, the kind of calories consumed may be key to maintaining weight loss because it impacts how efficiently individuals burn energy.
To assess the impact of calorie "quality" on weight maintenance, researchers at the New Balance Foundation Obesity Prevention Center at Boston Children's Hospital monitored 21 overweight and obese adults ages 18 to 40 from 2006 to 2010. The participants initially lost 10% to 15% of their body weight in the initial three months, when they all followed a diet that had 45% of total calories from carbohydrates, 20% from fat, and 25% from protein.
To assess how well common diets help individuals maintain weight loss, the researchers placed each participant on one of three diets for four weeks at a time, switching to the other diets in subsequent four-week periods. The three diets included in the study were:
A low-carbohydrate diet modeled on the Atkins plan;
A low-glycemic index diet modeled on Mediterranean cuisine; and
A low-fat diet modeled on one recommended by the American Heart Association.
The researchers found that the low-glycemic index diet—which draws about 40% of its calories from carbohydrates, 40% from fats, and 20% from protein—proved most effective at keeping weight off. In addition, participants on this diet burned about 150 calories a day more than those on the low-fat diet, without any adverse effects on cholesterol or hormone levels.
Though the low-carbohydrate diet seemed to help participants burn the most calories, the study found that it increased inflammation and production of stress hormone cortisol, risk factors for cardiovascular disease and diabetes.
Meanwhile, the researchers determined that the the low-fat diet was the least healthy. Participants on the diet burned fewer calories and experienced certain changes in metabolic factors typically associated with weight regain.
According to lead study author David Ludwig, "It's not that calories don't matter, but the quality of the calories going in can affect the number of calories going out" (Dooren, Wall Street Journal, 6/26; Gann/Albin, ABC News, 6/26).