Low-glycemic may be better than low-fat diet

Foods with a low-glycemic index, which are digested relatively slowly and cause smaller increases in blood sugar, may protect the heart and blood vessels better than low-fat fare, according to the findings of a small study.

Researchers in Boston found that when obese people consumed as many carbohydrates with a low-glycemic index as they wanted, they lost just as much weight in 12 months as people who stuck with a conventional, calorie-restricted low-fat diet.

Carbohydrates with a low-glycemic index include foods such as nonstarchy vegetables, fruit, legumes, nuts and diary products, according to the report in the American Journal of Clinical Nutrition.

Dieters who watched their glycemic indices also experienced a larger decrease in fatty substances in the blood linked to Heart disease and had a drop in levels of a protein that interferes with the body's ability to break down blood clots. In contrast, low-fat dieters had an increase in levels of the same protein, which may put them at higher risk of Heart Attack.

"Reducing (glycemic index) may be more effective than cutting back on fat over the long-term, both for weight loss and also for reducing risk of Heart disease," said study author Dr. David S. Ludwig.

"Based on our results, and several dozen other clinical trials and epidemiological studies, I would recommend" eating foods with a low-glycemic index, added Ludwig, who is based at Children's Hospital.

The glycemic index measures how efficiently the body can metabolize carbohydrates. It ranks carbohydrates by how much a person's blood sugar rises immediately after eating, and tends to favor high-fiber foods that take longer to digest.

Ludwig and his team asked 23 obese young adults to follow either a low-fat diet or a diet in which they ate low-glycemic index foods for one year. As part of the low-glycemic index diet, people could eat as much as they wanted of foods with a low index, and got roughly 45 to 50 percent of calories from carbohydrates, and 30 to 35 percent from fat.

Low-fat dieters cut their daily intake by 250 to 500 calories, limited fat to less than 30 percent of their total calories, and got between 55 and 60 percent of calories from carbohydrates.

Ludwig noted that even though low-glycemic index dieters had no calorie limits, they likely didn't overeat because they felt less hunger after eating foods that take longer to digest.

"Numerous previous studies by our group and by others have shown that individuals feel less hunger and greater (sense of fullness) after low-glycemic index compared to high-glycemic index meals," he added.

SOURCE: American Journal of Clinical Nutrition, May 2005.