Study cements low GI potential

07/06/05 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 reports of a study published in the American Journal of Clinical Nutrition.

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 non-starchy vegetables, fruit, legumes, nuts and diary products,

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.

Low glycemic index is a measure of how fast a carbohydrate is digested and glucose is released. Glucose is used as a reference and designated as 100. The glycemic indexes for all other carbohydrates are below 100. Foods with a glycemic index below 50 are called low glycemic foods. A food with a glycemic index bigger than 70 is called a high glycemic food. Low glycemic foods release glucose slowly.

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.