164 overweight or obese people participated in the study whose weights first were lowered by 12%. Then they were split into three different diet groups to maintain their weight. One group’s diet was high in carbs at 60% and 20% each in protein and fat. A second group was put on a diet of medium carbs and fat at 40% each and 20% protein. The third group’s diet was low in carbs and protein at 20% each with 60% fat.
“We found that the type of diet people ate had a major impact on their metabolism. Those on the low-carbohydrate diet burned about 250 calories a day more than those on the high-carbohydrate diet, even though all the groups were the same weight,” said Dr. David Ludwig, principal investigator of the study and co-director of the New Balance Foundation Obesity Prevention Center at Boston Children’s Hospital.
To maintain the baseline weight of the participants while on their specific diets, their calorie intake was either increased or decreased if they started to lose or gain weight.
One of the things that make maintaining your weight difficult is your diets’ direct effect on your metabolism.
“These findings show that all calories are not alike to the body from a metabolic perspective and that restricting carbohydrates may be a better strategy than restricting calories for long-term success,” Ludwig said.
He also believes that over a few years 20 pounds could be lost without the intervention of additional calorie intake for those on a low carb diet.
Naveed Sattar, professor of metabolic medicine at the University of Glasgow, who was not involved in the study, disagrees and advises caution because “the interpretation of the results seems quite incorrect.”
He bases his conclusion on previous larger and longer trials which have proven that weight change and weight loss “is broadly similar whatever diet one uses (low carb or low fat or others) as long as one sticks to the diet.” Sattar said.
Other experts voiced concern over the high intake levels of saturated fats in the low-carbohydrate diet, which could lead to increased risk levels of high cholesterol and heart disease.
Kevin McConway, emeritus professor of applied statistics at the Open University, noted that “because the different diets had to be made up from foods that may have differed in other ways than just their carbohydrate and fat content, it remains possible that these other differences were responsible for some part of the observed differences in energy expenditures.”