"Not all calories are alike": study says reducing carbohydrates instead of reducing weight

The 164-person study, published Wednesday by the medical journal BMJ, highlights the challenge of maintaining weight loss in the face of slowing hunger and the resulting metabolism, and says that the caloric effect of Low carbohydrate diet "could improve the success of obesity treatment. "

"These results show that all calories are different for the body and that limiting carbohydrates may be a better strategy for losing weight in the long run than limiting calories," said Dr. David Ludwig, co-author of the 39, study, co-director of the New Balance Foundation Obesity Prevention Center at Boston Children's Hospital.

The study addresses one of the most thorny problems in weight loss: As weight goes, the body responds, burns fewer calories and bombard us with hunger signals.

"It's the recipe for failure," Ludwig said.

It's also a mystery: why does the body react as if it were hungry when it obviously did not? For some researchers, including Ludwig, the answer lies in the carbohydrate-insulin model, the theory that processed carbohydrates such as white bread trigger hormonal changes leading to hunger, metabolic slowing, and weight gain.

Processed carbohydrates quickly digest into sugar, increasing insulin levels, Ludwig said. Insulin, in turn, programs fat cells to store excess calories. When calories are stuck in fat cells, the brain can not perceive them and thinks that the body needs more food.

The authors of the study collaborated with Framingham State University, where 164 overweight people – students, staff, faculty members, and community members – agreed to only eat foods that were being studied. First, study participants lost about 12% of their weight, or about 20 to 25 pounds for the average participant.

"We know that this will stress their metabolism," Ludwig said.

Then, for the 20-week test phase, study participants were randomly assigned to three groups: those who eat diets composed of 20% carbohydrate, 40% or 60%. Each diet contained 20% protein, the rest being fat. The diets used healthy foods and were as similar as possible, Ludwig said. The goal at this stage was to maintain weight loss, not to lose weight anymore.

Those who follow a low carbohydrate diet burn 209 to 278 more calories per day than those on a high carbohydrate diet, a difference that would lead to an estimated weight loss of 10 kilos over three years if researchers did not intervene to maintain their weight.

And the effect was even more important for those who were producing high levels of insulin in response to carbohydrates; they burned 308 to 478 more calories a day on a low carb diet than on a high carbohydrate diet.

How do you know if you are a high insulin secretor? "Look in the mirror," Ludwig advised. "If your fat distribution is mostly around the mid-section – so you look more like an apple than a pear – you're more likely to be a high secret agent of insulin."

Levels of physical activity were very similar for all three diet groups before the start of the study, Ludwig said.

The researchers encouraged all participants to maintain the usual level of physical activity monitored.

During the study, the low-carb group showed a tendency for more moderate to vigorous physical activity, possibly due to diet, Ludwig said via e-mail.

But he pointed out that exercise was only a minor component of the total effect on calories burned.

A co-author of a 2015 article in the journal PloS One comparing low-fat diets and carbs hailed the accuracy and design of the new study, including the direct calculation of energy expenditure, a difficult task and demanding in manpower.

"I think they've brought a level of sophistication that you do not tend to see in this type of testing," said Dr. Jonathan Sackner-Bernstein, former deputy director of the Center for Disease Control. Technology and Innovation of the Food and Drug Administration, which does consultation for drugs. and device companies.

Sackner-Bernstein said the study reinforced his belief that the more sensitive you are to carbohydrates, in terms of insulin response, the more important it is to have a restricted carbohydrate diet.

Ludwig said the findings of the study are very close to the authors' predictions, but much remains to be done.

"This is a study, so the results have to be replicated and examined in a wider population – although we have had a whole variety of demographics among our participants," he said. . "We need to see how this effect could play in other studies, how other populations would react."