By Ana Mantica, November/December 2009
Eating a meal made with “slow-release” carbohydrates, such as oatmeal or bran cereal, before you exercise may help you burn more fat, suggests a recent study in the Journal of Nutrition.
Researchers assessed the rate of fat burn among eight healthy women after they ate two breakfasts: muesli with milk, peaches, yogurt and apple juice on one day; cornflakes with skim milk, white bread with margarine and jam and an energy drink on another day. Both meals contained similar amounts of calories. The first breakfast (muesli) was a low-glycemic-index (GI) meal, the second was a high-GI meal. The glycemic index ranks foods based on how much they raise blood sugar. Lower-GI foods produce smaller spikes than higher-GI foods. Generally, foods that contain protein, fat and/or fiber—and are digested more slowly—fall lower on the GI scale than those that consist mostly of carbohydrate (e.g., white bread).
On the days when the women ate the low-GI breakfast, they burned nearly twice as much fat during a 60-minute walk as they did on the days when they ate the high-GI meal. Here’s why: because the muesli (low-GI) breakfast was more slowly digested, it didn’t spike blood-glucose levels as high as the cornflake (high-GI) breakfast did. In turn, insulin levels didn’t spike as high either—which probably explains why the muesli-eating women burned more fat, says Ian MacDonald, Ph.D., director of research at the University of Nottingham Medical School. Insulin plays a role in signaling your body to store fat. So, lower levels of insulin might help you to burn fat.
Bottom line: If you’re looking to burn more fat, pick low-GI foods, such as oatmeal, over high-GI foods, such as white toast, before your workout.