The Slow-Carb Diet

The Glycemic Index Equation

The glycemic index (GI) is a system of ranking carbohydrates based on how much they raise blood-glucose levels. It was originally developed for diabetics, but its usefulness has grown with our understanding of the impact blood-sugar levels have on hunger. According to Christine Pelkman, PhD, an assistant professor of nutrition at SUNY Buffalo, the theory goes: You eat a carbohydrate. The rise in blood sugar triggers a boost in insulin production. Insulin reduces your blood sugar, which leaves you feeling irritable and lethargic. You're left at Krispy Kreme's door, begging for a doughnut. "Falling blood-sugar levels can cause you to get hungrier faster," says Pelkman.

There are lots of things you can do to keep your blood-sugar levels balanced. Daily exercise helps, and so do regularly spaced snacks and meals, but your food choices are key. That's where low-GI foods come in. Foods with a GI lower than 55 raise blood sugar slightly, while those in the 55 to 70 range raise it a little higher; carbohydrates with a GI of more than 70 send it soaring. Low-GI foods have a more moderate effect on blood-sugar levels, primarily because they slow digestion -- that's why some low-GI plans call themselves "slow carb."

A number of studies show that a low-GI meal can be more satisfying than a high-GI meal and can help control overeating; some experts speculate that this effect may lead to weight loss. Research also shows that eating a low-GI diet may help prevent insulin resistance, which is a likely culprit in the development of diabetes. "Furthermore, since insulin resistance leads to excess weight gain around the waist, a known risk factor for cardiovascular disease, a diet based on low-GI foods may also be protective of your heart," says David Katz, MD, director of the Yale Prevention Research Center.