May 11, 2005 -- They ate all they wanted, yet lost weight.
They didn't avoid fats or carbs. They didn't count calories or eat prepackaged foods. Yet 11 obese 30-year-olds lost more weight than 12 of their peers on a conventional low-fat diet. And they lowered their risk of heart disease.
They didn't do it with a low-carb diet, but with a slow-carb diet. It's what nutritionists call a low-glycemic-load or a low-glycemic-index diet. The key is eating plenty of satisfying foods that your body can't quickly convert into sugar -- slow carbs, as they're coming to be called.
And it seems to work, says David S. Ludwig, MD, PhD, associate professor of pediatrics at Children's Hospital, Boston. Ludwig's small study appears in the May 1 issue of the American Journal of Clinical Nutrition.
"A diet focused on glycemic index may be easier to follow than diets restricted in either fat or carbs," Ludwig tells WebMD. "And there seems to be an additional benefit in reducing the risk of chronic disease."
Low-Glycemic Diet Made Simple
Foods have a higher or lower glycemic index (GI) depending on how much of them you eat, how you cook them, and what you eat them with.
This can quickly get complicated -- especially as it's not always easy to tell which foods are low-GI and which are high-GI. Ludwig's team came up with a simple plan. They created a low-glycemic-load food pyramid:
- At the bottom -- the basis of the diet -- are fruits and vegetables, cooked or served with healthful oils.
- Next come reduced-fat dairy foods, lean meats and fish, nuts, and beans.
- Higher up -- and meant to be eaten less frequently -- come whole grains, unrefined grains and pastas.
- At the top -- to be eaten sparingly if at all -- come refined grains, potatoes, and sweets.
Obese participants in the study were instructed to eat nonstarchy vegetables, fruits, beans, nuts, and dairy products. They were told to eat carbs with protein and healthful fat at every meal and snack. And they were told to eat until they were full and to snack when hungry.
Other obese study subjects were put on a traditional, low-fat/low-calorie diet. Both groups were asked to exercise regularly and were given lifestyle counseling.
"Those in the low-glycemic-diet group were told to eat as much as they wanted and to snack when hungry," Ludwig says. "Yet after a year, they lost fully as much weight as those told to cut back on fat and to cut back on calories. But they did better in terms of heart disease risk reduction."
Weight, Heart Risk Down
After 12 months on the diets, the slow-carb group lost 7.8% of their body weight compared with 6.1% in the low-fat-diet group.
Levels of a factor that increases blood clots - called plasminogen activator inhibitor - decreased by 39% in the slow-carb group but increased 33% among the low-fat dieters. Blood clots in the heart arteries are usually the cause of heart attacks.
Slow-Carb Diet, Not Low-Carb Diet
The Ludwig study is far from the first to find benefits for a low-glycemic-load diet, says Jennie Brand-Miller, PhD, professor of human nutrition at the University of Sydney, Australia, and co-author of The Low GI Diet Revolution and other books in The New Glucose Revolution series. Brand-Miller's editorial accompanies the Ludwig team's report.
"This study is telling us that losing weight on a low-GI diet produces better outcomes in terms of heart health than a conventional weight loss diet," Brand-Miller tells WebMD. "Even if the amount of weight lost is the same, you are better off on the low-GI diet. So it's a double bonus."
Brand-Miller says the slow-carb diet -- a name coined by Patricia and Harvey Haakonson, MD, authors of Slow Carb for Life -- is the opposite of the low-carb diet.
"The aim is not to get the lowest glycemic load possible. That's the fastest route to a low-carb-style diet," she says. "A low-GI diet and a low-carb diet are poles apart. We want you to eat lots of carbs, but selectively -- the low-GI versions."
How? Here's Brand-Miller's advice:
- Aim to eat carbohydrates at every meal.
- Aim for the low-GI breakfast cereals -- oats, muesli, All-Bran.
- Aim for heavy-grain breads, sourdough breads, and stone-ground breads.
- Eat lots of legumes (even baked beans).
- Don't be afraid to eat pasta, Basmati rice, or couscous.
- Have two to three servings of low-fat dairy a day.
- Eat nine servings of fruit and vegetables a day.
- Don't avoid any kind of fruit or vegetable except potatoes. Replace white potatoes with sweet potatoes, corn, and other healthy foods.
- Eat lean meat, fish, and chicken.
Ludwig now is recruiting volunteers for a larger study. He's looking for overweight or obese individuals aged 18 to 35 who are willing to sign up for 18 months. The study is taking place at Boston's Children's Hospital.