A study put three groups of dieters on different regimens. They included a low-fat group, a low-carbohydrate group that ate the same number of calories, and a third group on a similar low-carbohydrate plan that included 300 extra calories a day. The low-carbohydrate dieters lost more weight than low-fat dieters despite eating 25,000 extra calories over a 12-week study period. The findings generated national attention after Penelope Greene, a visiting scholar in the Harvard School of Public Health’s Nutrition Department, presented her research Oct. 13, 2003, at the annual meeting of the North American Association for the Study of Obesity, in Fort Lauderdale, Fla. Greene conducted the study with Walter Willett, Nutrition Department chair and Fredrick Stare Professor of Epidemiology and Nutrition. Participants in all three groups lost weight, Greene said, with the low-fat group losing an average of 17 pounds and the low-carbohydrate group that ate the same number of calories losing 23 pounds. The biggest surprise, however, was that the low-carbohydrate dieters eating extra calories lost more than those on the low-fat diet. Participants in that low-carbohydrate group lost an average of 20 pounds.