In one study, by Christopher Gardner, a professor of medicine at Stanford, patients were given low-fat or low-carb diets with the same amount of calories. After a year, weight loss was the same in each group, Gardner reported. Another study, by Dr David Ludwig of Boston Children’s Hospital, reported that a low-carbohydrate diet was better than a high-carbohydrate diet in helping subjects keep weight off after they had dieted and lost. The low-carbohydrate diet, he found, enabled participants to burn about 200 extra calories a day.