"A new study is raising questions about the ageold belief that a calorie is a calorie. Research from a new study funded by the National Institutes of Health finds that dieters were more successful maintaining weight on a lowcarb diet than they were on a lowfat diet. The research finds that dieters who were trying to maintain their weight loss burned significantly more calories eating a lowcarb diet than they did eating a lowfat diet. But some experts say these findings are very preliminary. The study funded by the National Institutes of Health httpcontent.usatoday.comtopicstopicOrganizationsGovernmentBodiesNationalInstitutesofHealth was designed to see if changing the type of diet people consumed helped with weight maintenance because dieters often regain lost weight.  So scientists had  obese participants ages  to  lose  to  of their initial body weight about  pounds. After their weight had stabilized each participant followed one of three different diets for four weeks. Participants were fed food that was prepared for them by diet experts. The dieters were admitted to the hospital four times for medical and metabolic testing. Heres a look at the three types of diets used in the new study A lowfat diet which is about  of calories from fat  from carbohydrates  from protein. It emphasizes wholegrain products and fruits and vegetables and cuts way back on oils nuts fatty meats and other highfat foods. A lowcarb diet similar to the Atkins diet with only  of calories from carbohydrates  from protein  from fat. This diet emphasizes beef fish chicken eggs cheese some vegetables and fruits while slashing the consumption of breads pasta potatoes rice cakes cookies and starchy vegetables. A lowglycemic index diet similar to a Mediterranean diet is made up of vegetables fruit beans healthy fats olive oil nuts and mostly healthy grains oldfashioned oats brown rice. It gets about  of daily calories from carbohydrates  from fat and  from protein. Source Journal of the American Medical Association  The diets had the same number of calories but the fat protein and carbohydrate content varied. Those diets A lowfat diet which was about  of calories from fat and emphasized wholegrain products and fruits and vegetables. A lowcarb diet similar to the Atkins diet with only  of calories from carbohydrates. It emphasized fish chicken beef eggs cheese some vegetables and fruits while eliminating foods such as breads pasta potatoes and starchy vegetables. A lowglycemic index diet similar to a Mediterranean diet made up of vegetables fruit beans healthy fats olive oil nuts and mostly healthy grains oldfashioned oats brown rice. These foods digest more slowly helping to keep blood sugar and hormones stable after the meal. Findings published in this weeks Journal of the American Medical Association Participants burned about  calories more a day on a lowcarb diet than they did on a lowfat diet. Thats the amount youd burn off in an hour of moderate intensity physical activity without lifting a finger says senior author David Ludwig httpcontent.usatoday.comtopicstopicDavidLudwig director of the New Balance Foundation Obesity Prevention Center at Boston Childrens Hospital. Participants burned  calories more on the lowglycemic index diet than the lowfat diet. Thats about an hour of light physical activity he says. The reason for the lowcarb advantage is unclear he says. We think the lowcarb and lowglycemic index diets by not causing the surge and crash in blood sugar dont trigger the starvation response. When the body thinks its starving it turns down metabolism to conserve energy he says. The authors note a downside to the lowcarb diet It appears to raise some risk factors for heart disease. Ludwig says that restricting carbohydrates over the long term may be hard for many people. If youre trying to lose weight you can get a jump start with a lowcarb diet but over the long term a lowglycemic index diet may be better than severely restricting carbohydrates. The lowglycemic index diet seems to be the happy medium says Cara Ebbeling associate director of the Obesity Prevention Center. It didnt slow metabolism as much as the lowfat diet and it didnt seem to have some of the negative effects on cardiovascular disease risk. On a lowglycemic index diet you would avoid highly processed carbs such as white bread white rice many snack foods prepared breakfast cereals sugary desserts and sugary beverages she says. Experts had different responses to the findings. George Bray an obesity researcher at Pennington Biomedical Research Center in Baton Rouge who has also studied this topic and who wrote the accompanying editorial in JAMA says that other studies show that you can do well on any diet as long as you stick to it. Adherence is the major key for weight loss and maintenance. There is no magic in any diet. Eric Westman a Duke University httpcontent.usatoday.comtopicstopicOrganizationsSchoolsDukeUniversity researcher who has conducted several studies on the lowcarb diet and is coauthor of The New Atkins for a New You says this study documents that the lower the carbohydrates the better the metabolic effects. People burn more calories if they eat fewer carbohydrates. Marion Nestle httpcontent.usatoday.comtopicstopicMarionNestle a nutrition professor at New York University httpcontent.usatoday.comtopicstopicOrganizationsSchoolsNewYorkUniversity says longer studies conducted among people in their own environments not with such controlled meals have shown little difference in weight loss and maintenance between one kind of diet and another. More research is needed to show that interesting results like these are applicable in real life she says. In the meantime if you want to lose weight eat less."