The most healthful time to eat is just before or after you exercise. When you eat any source of sugar, it is used for energy and a small amount is stored in your muscles and liver. All the rest is turned into a fat called triglycerides that is stored as fat, forms plaques in your arteries and blocks insulin receptors which can cause diabetes. One study showed that exercise prevents the rise in triglycerides that follows eating sugar (Diabetes, May 14, 2013). Another showed that exercising after eating sugar prevents the expected sharp rise in blood sugar levels and the high rise in insulin that can constricts arteries to cause heart attacks (J Atheroscler Thromb, April 19, 2013).
How Exercise Protects You
Every cell in your body is like a balloon full of fluid. A high rise in blood sugar after eating causes sugar to stick to the outer surface membranes of cells. Once there, sugar cannot get off the cell. It is eventually converted to sorbitol that destroys the cell to cause every known side effect of diabetes: heart attacks, strokes, blindness, deafness, dementia, impotence, loss of feeling and so forth. Many North Americans suffer very high rises in blood sugar even though they have never been diagnosed as being diabetic.
Resting muscles draw almost no sugar from the bloodstream, Contracting muscles draw sugar from the bloodstream without even needing insulin. The harder you exercise, the more sugar muscles pull out of the bloodstream. This effect is maximal during intense exercise, diminishes rapidly one hour after you finish exercising and disappears completely after about 17 hours. If you eat before you exercise or within an hour after you finish exercising, your muscles are far more sensitive to insulin and can draw sugar far more rapidly from the bloodstream.
Exercising After Eating Rarely Causes Stomach Cramps
Many people believe that they should not exercise immediately after eating because they remember mothers’ warnings that they would get stomach cramps. Exercising is only likely to cause stomach cramps if you are out-of-shape or eat way too much.
Exercise causes your heart to pump a large amount of blood to your muscles. Putting food in your stomach causes your stomach muscles to contract vigorously which increases blood flow to your stomach. Fit people have hearts that can easily pump blood simultaneously to both the stomach and skeletal muscles. Long distance bicycle racers, runners and cross country skiers eat very large amounts of food during races and virtually never suffer belly cramps. These athletes often have training runs that last many hours and they have to eat just to keep up their blood sugar levels during training. Otherwise they would pass out from low blood sugar because they don’t have enough sugar for the brain to function.