"We've found that, contrary to nutritional dogma, all calories are not created equal," said David Ludwig, director of the New Balance Foundation Obesity Prevention Center Boston Children's Hospital, USA – and a co-author of the study.
Writing in JAMA, the team of US-based researchers examined the effects of three different diets – differing widely in macronutrient composition and glycemic load – on energy expenditure following weight loss.
Led by Dr Cara Ebbeling the scientists performed a controlled 3-way crossover trial involving 21 overweight and obese young adults – finding that resting energy expenditure and total energy expenditure were reduced more with a low-fat diet or low–glycemic index diet compared to a very low-carbohydrate diet, despite all participants consuming the same amount of calories.
"Total calories burned plummeted by 300 calories on the low fat diet compared to the low carbohydrate diet, which would equal the number of calories typically burned in an hour of moderate-intensity physical activity," he explained.
The researchers suggest that a strategy to reduce glycemic load rather than dietary fat may be advantageous for weight-loss maintenance and cardiovascular disease prevention.
“Ultimately, successful weight-loss maintenance will require behavioral and environmental interventions to facilitate long-term dietary adherence. But such interventions will be most effective if they promote a dietary pattern that ameliorates the adverse biological changes accompanying weight loss," they conclude.
Commenting on the research via her Food Politics blog, Professor Marion Nestle of New York University, USA, noted that if the results of the new research are correct, people eating high-fat, low-carbohydrate diets are likely to have the easiest time maintaining weight loss.
“In contrast, people on low-fat, high-carbohydrate diets are likely to have a harder time maintaining weight loss,” she said.
The study challenges the notion that ‘a calorie is just a calorie’ from a metabolic point of view by suggesting that a low-glycemic load diet is more effective than conventional approaches at burning calories at a higher rate after weight loss.
