Prepared Foods July 4, 2005 enewsletter

Dietary carbohydrates with low glycemic index (GI, the relative effect of a given carbohydrate on rise in blood glucose compared with simple sugar) are known to increase satiety while improving serum lipid profiles.

Furthermore, increased serum triacylglycerol concentrations are associated with excessive high-GI foods and are known to be associated with cardiovascular risk, potentially by increasing concentrations of plasminogen activator inhibitor 1 (PAI-1), a factor that promotes clotting in coronary blood vessels.

Reporting in the American Journal of Clinical Nutrition, Ludwig and colleagues at Harvard University compared the effects of low-GI diets taken ad libitum with those of a conventional low-fat, restricted-calorie diet in 23 moderately obese young adults with a mean age of 27-29 years, who were followed by behavioral modifications and dietary evaluations at frequent intervals for 12 months.

Although the individuals in the low-GI group (n=11) consumed their diets ad libitum, their decrease in caloric intake and overall weight loss of 6%-8% matched that of the 12 individuals in the conventional low-fat, calorie-restricted group. Moreover, the low-GI group experienced a decrease in serum triacylglycerol concentrations with a 39% decrease in PAI-1 concentrations, compared with a 33% increase in PAI-1 in the conventional low-fat diet group.

The authors concluded that the ad libitum low-GI diet is beneficial because it increases satiety and decreases body weight at the same time that it reduces serum triacylglycerol concentrations and cardiovascular risk.

An accompanying editorial by Brand-Miller reviewed other studies that showed the benefits of a low GI on lipid profiles and cardiovascular risk and stressed the health importance of low-GI diets containing whole grains and fiber compared with high-GI diets composed of highly refined processed foods (Ebbeling CB, Leidig MM, Sinclair KB, et al., “Effects of an ad libitum low-glycemic load diet on cardiovascular disease risk factors in obese young adults.” Am J Clin Nutr 2005;81:976-82; Brand-Miller J. “Optimizing the cardiovascular outcomes of weight loss.” Am J Clin Nutr, 2005;81:949-50).