Disputing the import of glycemic index.

There is much debate over the importance of a given food's GI. Many experts think the variations in the speed of carbohydrate conversion to glucose among foods are too slight to effect weight loss. Even the American Diabetes Association does not distinguish between carbohydrate-rich foods with low or high Gls, but equivalent organizations in Australia and Canada do.

It's important to consider a food's glycemic load (GL)--the amount of carbohydrate it contains--when weighing the importance of how rapidly it converts to glucose (its GI). Dr. Lupton says factoring in only how quickly a food converts to glucose "makes the poor carrot one of the foods with the highest glycemic index." But after GL, she notes that "the carrot doesn't look so bad, because even though its carbohydrate is glycemic, it doesn't have that much carbohydrate in a serving."

Dr. Lupton adds that the GI scale is further limited by failing to take other nutritional factors into account. "Any scale that has a slice of cheese pizza coming out better than a carrot in terms of human health is not one that most nutritionists would promote," she says. Yet to some degree, it would seem that avoiding foods with both a high GI and GL helps to avoid undesirable peaks and valleys in blood-sugar level, and therefore energy, throughout the day.