The glycemic index measures how much a fixed quantity of different foods raises your blood-sugar levels compared with a standard, pure glucose (GI=100). Foods with a high GI value (greater than 70) tend to cause a higher spike in blood sugar—and in insulin, the hormone that helps glucose get into cells. The spikes are especially problematic for people with diabetes, who lack an effective insulin system to clear the sugar from their blood. And, because high-GI foods are so quickly metabolized, they tend to make you hungry again sooner, says David Ludwig, M.D., Ph.D., a Harvard endocrinologist and author of Ending the Food Fight (Houghton Mifflin, 2007). Ludwig’s research found that obese teenage boys were hungrier after they’d eaten a high-GI breakfast of instant oatmeal, and ate 600 to 700 calories more at lunchtime than when they’d breakfasted on moderate- or low-GI meals like steel-cut oats or omelets.
By contrast, lower-GI foods (under 55) are metabolized more slowly, and are believed to keep your appetite on a more even keel. Some experts think that by tempering blood-sugar surges, eating low-GI foods may even help prevent the damage to cells that’s caused by high blood-glucose concentrations.
Following the glycemic index (GI) system can be confusing—“but only if you spend too much time crunching numbers and not looking at the big picture,” says Joyce Hendley, EatingWell’s nutrition editor and author of The EatingWell Diabetes Cookbook (The Countryman Press). Knowing a few overall principles can make low-glycemic eating much simpler, she explains:
1. Bigger is better.
Large food particles take longer for the body to break down and absorb, so they move more slowly through your digestive system. So in general, the more intact and less processed a food is, the lower its GI. Think whole rather than refined grains, whole fruit rather than fruit juice, steel-cut oats rather than instant oatmeal and stone-ground rather than plain cornmeal. When buying whole-grain bread choose stone-ground, sprouted or cracked-wheat types; the grain kernels should be visible.
2. Fiber up.
By definition, fiber is the part of plant foods that cannot be digested by the body, so fiber-rich foods like beans, nuts, dried fruits and high-fiber cereals, pasta and breads are inherently low on the GI. Focus on boosting fiber by eating more foods like these and you won’t have to think about GI.
3. Pair with protein.
When it has protein to break down, the stomach empties more slowly. Adding a little protein to a carbohydrate-based meal or snack—say, adding a few chicken strips and a sprinkle of cheese to your pasta bowl, or a light smear of peanut butter on your toast—can lower the GI value of your meal.
4. Drizzle on a healthy fat.
Like protein, fat molecules also slow down digestion, so including a little fat can lower a food’s GI and make it more satisfying. Be sure to choose heart-healthy unsaturated fats like vegetable oils and nuts. And, if you’re watching calories, be moderate: drizzle bread with a little olive oil, toss carrots with a bit of tasty dressing, sprinkle slivered almonds on your salad.
Following low-GI eating principles can help people with diabetes fine-tune their blood-sugar responses and may even help people with prediabetes lower their risk of progressing to full-blown disease. New research connects low-GI diets with lower risk of age-related macular degeneration, a major cause of blindness, and other work suggests a possible link with reducing risk for heart disease and even colorectal cancer.
And of course, there’s the tantalizing possibility that by its moderating effects on blood sugar and thus appetite, eating a low-GI diet may help people lose weight. Unfortunately, research results in this area have been mixed. Ludwig has found that low-GI diets seem to be most effective in people whose bodies secrete more insulin: more often “apple-shaped” people, who accumulate extra fat around their waists, compared to people with lower-body fat (“pear shapes”). “Apple-shaped people who have done poorly on traditional low-fat diets may do especially well on a low-glycemic-load diet,” he says. And, regardless of body shape, those who followed low-glycemic diets improved their triglyceride and HDL cholesterol levels, he added; both are important risk factors for heart disease.
Chambers Health 