To do the new study, Dr. Ludwig and his colleagues collaborated with Framingham State University, about 20 miles outside Boston, where they recruited overweight students, staff members and faculty members. Each participant went through two phases of the study. First, they were put on strict diets that lowered their body weight by about 12 percent, which was designed to stress their metabolisms.
“At that point their bodies are trying to regain the weight,” Dr. Ludwig said. “It pushes the body and predisposes to weight regain.”
In the second phase of the study, the subjects were assigned to one of three diets with 20 percent, 40 percent or 60 percent of their calories from carbohydrates. Protein was kept steady at 20 percent of calories in each diet.
Over the next five months, the researchers tracked the subjects meticulously and provided them with enough daily meals and snacks to keep them from losing or gaining any weight. This was so the researchers could determine precisely how the subjects’ metabolisms responded to the different diets while their body weight remained stable.
The researchers tracked biomarkers that helped them ensure that the participants stuck to their diets. They also worked with a large food service company, Sodexo, to prepare thousands of generally healthful meals that the subjects could eat in cafeterias or take home with them. A typical meal for the high-carb group might consist of a chicken burrito bowl with rice and vegetables, for example, or roasted turkey with green beans and mashed potatoes. The low-carb group would get a similar meal with fewer carbohydrates, like a chicken burrito lettuce wrap or roasted turkey with green beans and mashed cauliflower.
What the researchers found was striking. The roughly 250 extra calories that the subjects in the low-carb group burned each day could potentially produce a 20-pound weight loss after three years on the diet, Dr. Ludwig said. People who tended to secrete higher levels of insulin did the best on the low-carb diet, burning about 400 extra calories a day.
The subjects on the low-carb diet also had the sharpest declines in a hormone called ghrelin, which is produced in the stomach. Ghrelin promotes hunger and body fat, and it lowers energy expenditure. Suppressing ghrelin may be one reason the low-carb diet increased metabolism, the authors noted.
Source : https://www.nytimes.com/2018/11/14/well/eat/how-a-low-carb-diet-might-help-you-maintain-a-healthy-weight.html406