Nov. 23, 2004 -- One of the pitfalls of dieting is that it decreases your metabolism, making it harder to burn calories. But focusing on foods that minimally affect blood sugar may be key to keeping your metabolism revved up.
A new study shows that dieters who decreased calories while concentrating on healthy fats and carbohydrates had higher metabolisms after 10 weeks of dieting. They also reported less hunger than dieters taking in the same number of calories who ate only low-fat foods.
The two groups lost similar amounts of weight. But the findings offer early evidence that eating a so-called low-glycemic diet may overcome the body's natural tendency to slow metabolism when calories are restricted. A low-glycemic diet emphasizes healthy fats and carbohydrates.
The findings are reported in the Nov. 24 issue of the Journal of the American Medical Association.
"Almost anyone can lose weight in the short term -- very few keep it off in the long term," researcher David S. Ludwig, MD, PhD, says. "That has given rise to the notion that the body has a 'setpoint' and that when you diet internal mechanisms work to restore your weight to that setpoint. A low-glycemic-load diet may work better with these internal biological responses to create the greatest likelihood of long-term weight loss."
No Bad Food Groups
The low-glycemic diet is now widely recommended for people who are at high risk for developing type 2 diabetes. Several very popular commercial weight loss plans, including the South Beach diet and Sugar Busters, are based on it.
Instead of banning whole food groups, the diet restricts carbohydrates that are rapidly digested and spike blood sugar and insulin levels. Carbohydrates, such as refined sugar, white bread, white rice, potatoes, fruit juices, and many commercial breakfast cereals are restricted on the diet. These carbohydrates are more likely to leave you feeling hungry shortly after eating.
Whole grains, fruits, vegetables, nuts, and legumes are encouraged in a low-glycemic diet. These foods typically leave you feeling full longer.
The newly published study involved 46 overweight or obese adults who reduced calories while eating either a low-fat or low-glycemic index diet. Both diets provided approximately 1,500 calories a day and were designed to produce a 10% weight loss within six to 10 weeks.
A typical breakfast for the low-fat dieters might include instant oatmeal with skim milk and raisins. Steel-cut oats with blueberries and 2% milk would be substituted for the low-glycemic-load dieters.
Thirty-nine of the dieters lost 10% of their body weight during the study. Resting metabolism of low-glycemic load dieters slowed at about half the rate of low-fat dieters. The low-glycemic group burned about 80 calories more per day than their low-fat counterparts.
The low-glycemic dieters also reported having less hunger. They also had greater improvements in risk factors associated with diabetes and heart disease, including blood pressure, triglyceride levels, and chronic inflammation.
'The Perfect Compromise'
Ludwig tells WebMD that the findings show that a healthy, balanced eating plan offers advantages over fad diets for weight loss.
"For many years we had the low-fat paradigm. It made sense that if you didn't want fat on your body you shouldn't put fat in your body. But the problem was that it didn't seem to work very well and even had some adverse side effects," he says. "In the past few years the pendulum has swung very far in the other direction with the assumption that all carbohydrates are bad."
Ludwig says that while carbohydrate-limiting diets have been proven to promote short-term weight loss, two recent studies show that these dieters tend to regain the weight they lose.
"Both the low-fat and low-carbohydrate approaches are probably too restrictive," he says. "The low-glycemic load approach is the perfect compromise. A diet based on glycemic load may work with the body's own mechanism to allow people to eat a wider range of foods and fill up sooner."
Nutritionist Karmeen Kulkarni, RD, MS, says the low-glycemic-load diet represents a healthy approach to eating. But she adds that Ludwig's study was too small and too short to confirm that it is better than other weight loss approaches. Kulkarni is president-elect of health care and education for the American Diabetes Association.
"These participants were followed very closely and all of their food was weighed and measured, so it is not surprising that they lost weight," she says. "Certainly these findings need to be confirmed in larger, longer studies that do not so closely control food intake."
Ludwig's research team is currently recruiting patients for just such a study, and he hopes to follow participants for a year and a half. Boston residents between the ages of 18 and 35 can learn more about participating in the study by calling (617) 355-2500.