If you're dieting, you know you've got to count calories, carbs and fats. But if you really want to take off the weight and keep it off, you might want to pay more attention to the glycemic index, which is essentially a measure of how quickly foods are digested.
That's because high glycemic foods cause a surge in blood sugar, followed by a crash. That biological reaction releases hormones that stimulate hunger and, according to David Ludwig of the New Balance Foundation Obesity Prevention Center at Boston Children's Hospital, actually lower metabolism, adding up to a dismal recipe for people who want to lose weight and keep it off.
"One of the unfortunate aspects of weight loss maintenance is that it takes fewer and fewer calories to just stay the same," Ludwig says. "As the body loses weight, it becomes more efficient and requires fewer calories," making it harder and harder to continue losing and making it difficult to maintain weight loss without continually dieting. By some estimates, only 1 in 6 Americans who lose weight are able to keep it off after one year.
But Ludwig and colleagues recently published a study in the Journal of the American Medical Association that offers some tools you might use to fight back. Researchers compared the low-carb, low-fat and low-glycemic diets to see which one burned the most calories per day. The low-carb diet was the clear winner. The low-fat diet was the loser. But it was the diet in the middle, the low-glycemic index diet, that Ludwig suggests is more promising. It burned more calories per day than the low-fat diet and proved easier to stick to over the long term than the low-carb diet.
Mike Rogers, 43, was a participant who managed to keep off the 40 pounds he lost. He says the difference in the three diets was "enormous," adding that "the low-glycemic diet reminded me of the way my mom and grandmom cooked while I was growing up; I felt far better on the low-glycemic diet than on either of the other two."
Still trim, Rogers now eats far more fruits and vegetables than he did in the past, and, when it comes to carbohydrates, he opts for those with a lower glycemic index. That means brown rice versus white, whole grain pasta and steel cut oats instead of "quick-cooking" oats. He pretty much stays away from all processed foods.
Highly processed and refined foods, like packaged items, white bread, white rice, prepared breakfast cereals and crackers have a high glycemic index. "The body can digest these foods into sugar literally within moments after eating," says Ludwig.
Low-glycemic foods tend to be natural foods like most vegetables and fruits, nuts, beans and whole grains. They actually wend their way slowly through the body's digestion system, using up more energy and burning more calories in the process. And, best of all, says Ludwig, they actually "increase the metabolic rate and decrease hunger, giving us a biological advantage" in losing and maintaining weight.
Ludwig is quick to caution that his study was short and not conclusive. He's working now to design a long-term study that looks at diet and weight loss maintenance over a number of years.
Registered dietitian Joy Dubost, a spokesperson for the Academy of Nutrition and Dietetics, says the low-glycemic diet is hard to follow. In large part, that's because there are many factors that affect how the body digests food, including the combination of food we eat, food preparation, whether vegetables and fruits are ripe, and our individual differences in how we digest food.
And eating too many low-glycemic foods that are also high in calories, sugar or saturated fats can be problematic.
Dubost urges moderation of carbs and fats. But equally important, she says, is a "part of the equation often ignored": exercise. She points to research that shows people who were successful in maintaining their weight a year after losing it added a significant ingredient to their daily regimen: at least 60 to 90 minutes of moderate exercise every single day.
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Today in Your Health, an American epidemic of kidney stones.
INSKEEP: Doctors see a link between that problem and obesity. And we begin with ways to maintain a healthy weight. Some people count calories, carbs and fats. And some researchers think you should look at the glycemic food index. If you're wondering what's that, listen to NPR's Patti Neighmond.
PATTI NEIGHMOND, BYLINE: Here's the premise. Not all calories are alike. Obesity specialist Dr. David Ludwig with Boston Children's Hospital.
DR. DAVID LUDWIG: Simply focusing on the calorie content of food ignores a key notion, which is that foods affect blood sugar and hormones in dramatically different ways based on their composition.
NEIGHMOND: For example, some foods are slow to digest, like most fruits, nuts and vegetables. They take their time wending their way through the digestive system. And that means they use up more energy and calories. Other foods zip through our system rapidly.
LUDWIG: White bread, white rice, potato products, prepared breakfast cereals are all made up of sugar in a long chain. And the body can digest these foods into sugar in literally moments after eating.
NEIGHMOND: That quick digestion causes a surge of blood sugar and then a crash. That makes us feel hungry pretty quickly after eating. But with slow foods we feel satisfied longer. Here's Mike Rogers, who took part in a study headed by Dr. Ludwig. Rogers was all excited when part of his diet plan one night included a big pile of mashed potatoes.
MIKE ROGERS: Then I went and looked at the clock, because I was hungry again, figuring that it must be time for me to eat my snack. And I said, that can't be right. When did I - and I realized that it had been almost no time at all since I had finished this enormous plate of mashed potatoes.
NEIGHMOND: The reason Rogers was hungry so quickly is because potatoes, like corn and a few other vegetables, have a high glycemic index. So do most refined and processed foods. They're digested quickly, causing that surge, then crash, of blood sugar. Not only that, Ludwig says, high glycemic foods slow down metabolism.
LUDWIG: One of the most unfortunate aspects of weight loss maintenance is that it takes fewer and fewer calories to just stay the same, let alone keep losing weight. That as the body loses weight, it becomes more efficient and requires fewer calories.
NEIGHMOND: Ludwig recently completed his diet study, which compared low-carb, low-fat and low-glycemic diets. He found the low-carb diet burned the most calories, but it was hard to stick to. The most promising diet turned out to be the low-glycemic one. People like Mike Rogers were able to lose weight and keep it off. Rogers maintained a 40 pound weight loss by shifting to low-glycemic foods that are mostly natural and unprocessed.
ROGERS: I eat a lot less white rice and a lot less potatoes than I used to eat. And the other thing that I learned that I liked quite a bit was steel cut oats. I've never been a big fan of standard oatmeal, but steel cut oats has enough tooth in it that I really enjoy that.
LUDWIG: Dr. Ludwig is quick to caution his study was short and not conclusive. He's working now to design a long term study that looks at diet and weight loss maintenance over a number of years.
NEIGHMOND: Joy Dubost is a registered dietitian with the Academy of Nutrition and Dietetics. She says the problem with the low-glycemic diet is that it can be confusing because lots of factors affect how the body digests food.
JOY DUBOST: Factors like ripeness, the variety of the products, the way it was prepared, the types of sugar that are present or carbohydrates, the amount of fiber and fat present and just the way your body digests it.
NEIGHMOND: And eating too many low-glycemic foods that are also high in calories, sugar or saturated fats can also be a problem. Dubost urges moderation of carbs and fats. And equally important, the other end of the equation - exercise. She points to a study which found people who successfully maintained their weight loss added 60 to 90 minutes of moderate exercise every single day.
Patti Neighmond, NPR News. Transcript provided by NPR, Copyright NPR.