Will munching raw carrots make you fat? Is enjoying a fluffy baked potato a no-no? If you believe the claims about glycemic index made in certain diet books, you may be eliminating these foods. But it's not that simple. First, some background.
Glycemic index (GI) was developed in the early 80's by diabetes researchers. Their discoveries rocked the nutrition world when they found that some foods raise blood sugar as quickly as table sugar does.
Glycemic index measures how high blood sugar rises after eating 50 grams of carbohydrates from a particular food. The higher the glycemic index, the greater the blood sugar response.
Foods high on the list include raisins, rice cakes, instant mashed potatoes, plain bagels, white rice, and corn flakes. Lower glycemic foods are garbanzo beans, brown rice, green lentils, whole grain pumpernickel bread, most dairy products, and semolina pastas.
While glycemic index is the blood sugar-raising power of a food, glycemic load (GL) takes serving size into account. Instead of testing the amount of food that contains 50 grams of carbohydrates, it tests a normal serving size, regardless of how many grams of carbs it contains. This results in a more realistic measurement, which tends to be lower than a food's glycemic index.
But GL values are not always predictable. Many factors come into play, including the amount of protein, fat and fiber, as well as the cooking and processing methods. To further complicate matters, the effects of a high GL diet vary greatly between people, depending on body weight and level of physical activity.
What about those crunchy carrots that you used to snack on? The ones you heard are so high in sugar? In order to eat a 50 gram carbohydrate portion, you'd have to consume a pound of them.
So what's the value in knowing a food or meal's glycemic index? According to supporters, plenty. Some researchers claim it can influence the risk of obesity, type 2 diabetes, heart disease and even cancer. But critics contend the jury is still out.
Glycemic index, by itself, is irrelevant, since we don't usually eat isolated foods. We eat them in the content of a meal. A food's GI is influenced by how it's prepared and what else is eaten with it.
Yet the glycemic index concept may be a useful tool for choosing meals that help you avoid a spike in blood sugar and the resulting rush of insulin that causes you to eat more calories later on. But there is no proof that eliminating foods with a higher GI promotes weight loss.
What to do now? Avoid mostly carbohydrate meals or starches without any fiber (like a large bagel for breakfast). Select a balanced diet from a variety of foods, with a focus on nutrient-dense vegetables, fruit, low fat dairy, and lean proteins, which will naturally provide you with a low glycemic load. Choose foods that are closer to their natural state over those highly processed (old-fashioned oatmeal instead of instant, or whole grain crackers instead of white.) Remember, it's the overall diet that counts and not individual foods.
About Christine Palumbo, RD
Christine Palumbo, MBA, RD has been a nutrition communications consultant since 1989, providing dietary counsel and analysis on various nutrition, health and weight management topics to corporate clients and news media outlets nationwide. An active member of the American Dietetic Association (ADA), the Illinois Dietetic Association and the Chicago Dietetic Association for more than twenty years, she has served on a variety of boards and practice group committees within those organizations.
Palumbo has been featured in national women's, health and business magazines, daily newspapers and local and national radio and television programs. She also received the Illinois Dietetic Association's Outstanding Dietitian of the Year award for 2002.