June 27, 2012
Low-Glycemic Diet Best For Maintaining Weight Loss
Lawrence LeBlond for redOrbit.com
Diets based on healthy carbohydrates and not on low-fat may offer dieters a better chance of burning calories and keeping weight off and without unwanted side effects, according to a new study published Tuesday in the Journal of the American Medical Association.The research suggests that dieters trying to maintain weight loss burned significantly more calories eating a carb-healthy diet rather than a low-fat diet, but some experts say the results are still preliminary.
The National Institutes of Health-funded study, led by Cara Ebbeling, PhD, associate director and David Ludwig, MD, director of the New Balance Foundation Obesity Prevention Center Boston Children´s Hospital, found that diets that reduce the surge in blood sugar after a meal (low-glycemic index or very-low carb) may be more beneficial to those trying to achieve lasting weight loss.
Participants in the study who followed a low-glycemic-index diet, which includes fish, fruit, vegetables, nuts and whole grains, also saw improved cholesterol levels and other important markers that lower the risks of developing heart disease and diabetes. The researchers said that foods such as minimally processed oatmeal, almonds, brown rice, beans and healthy fats like olive oil, and other similar foods also offer beneficial results.
Furthermore, the study found that the low-glycemic diet had similar metabolic benefits to the very-low-carb diet without negative effects of stress and inflammation as seen by participants consuming the foods in the very-low-carb diet.
Ludwig explained that most people struggle to keep weight off. Previous studies have shown that weight loss reduces the body´s daily energy expenditure (how many calories the body burns through activity and just by resting) making it easy to regain weight.
The study´s 21 participants, who ranged in age from 18 to 40 years old, lost 10 to 15 percent of their body weight during the three-month diet that contained about 45 percent of total calories from carbohydrates, 30 percent from fat, and 25 percent from protein.
One month after the weight-loss phase of the study, the participants were each placed on one of the three diets: low-fat, very-low-carb, and low-glycemic-index. The participants were then switched to the other two diets during two additional four-week periods.
The low-fat diet consisted of about 20 percent calories from fat, 60 percent from carbs, and 20 percent from protein; the low-carb diet consisted of 10 percent of calories from carbs, 30 percent from proteins, and 60 percent from fat; and the low-glycemic diet was made up of 40 percent calories from carbs, 40 percent from fat, and 20 percent from protein.
Each of the three diets fell within the normal healthy range of 10 to 35 percent of daily calories from protein.
Even though the very-low-carb diet produced the greatest improvements in metabolism, it also produced an undesirable side-effect: increasing cortisol levels, which can lead to insulin resistance and cardiovascular disease. It also raised C-reactive protein levels, which may also increase the risk of cardiovascular disease.
And although a low-fat diet is traditionally recommended by the US government and the American Heart Association, it caused the greatest decrease in energy expenditure, an unhealthy lipid pattern and insulin resistance.
Based on these findings, the researchers suggest that a low-glycemic load diet is more effective than conventional approaches at burning calories.
“From a metabolic perspective our study suggests that all calories are not alike,” Ludwig told WebMD. “The quality of the calories going in is going to affect the number of calories going out.”
“Total calories burned plummeted by 300 calories on the low fat diet compared to the low carbohydrate diet, which would equal the number of calories typically burned in an hour of moderate-intensity physical activity,” he added.
“In addition to the benefits noted in this study, we believe that low-glycemic-index diets are easier to stick to on a day-to-day basis, compared to low-carb and low-fat diets, which many people find limiting," added Ebbeling. “Unlike low-fat and low-very-carbohydrate diets, a low-glycemic-index diet doesn´t eliminate entire classes of food, likely making it easier to follow and more sustainable.”
“The low-glycemic index diet seems to be the happy medium,” she said. “It didn´t slow metabolism as much as the low-fat diet, and it didn´t seem to have some of the negative effects on cardiovascular disease risk.”
The study results received mixed reviews from other health experts.
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,” noted George Bray, an obesity researcher at Pennington Biomedical Research Center in Baton Rouge, who wrote an accompanying editorial in JAMA.
Eric Westman, a researcher at Duke University who has conducted several studies on the low-carb diet, said the study documents that the “lower the carbohydrates, the better the metabolic effects. People burn more calories if they eat fewer carbohydrates.”
Marion Nestle, a nutrition expert at New York University, referred to other studies conducted among people in their own environments, and not with controlled meals, that have shown “little difference in weight loss and maintenance between one kind of diet and another.” She feels more research is needed to show that interesting results like these are applicable in real life, and not just in a controlled environment.
Elisabetta Politi, MPH, nutrition director of the Duke Diet and Fitness Center in Durham, NC, agreed that more research is needed, but finds the results intriguing. “The idea that the type of calories people take in has a direct impact on the amount of energy they expend is certainly intriguing and worth exploring further,” she told WebMD.
Since participants were only followed for three months and were on highly-controlled eating plans, it is not clear if one diet really is better than another for maintaining weight loss, Politi said. “It makes sense that people would be able to stick with a low-glycemic-index diet better because it is less restrictive, but that wasn´t really shown in this study,” she added.