Exercising on an Empty Stomach Can Both Prevent and Treat Diabetes
One of three North Americans will become diabetic because they eat a high-calorie, high-fat diet that:
- blocks insulin receptors
- to prevent cells from responding to insulin (insulin resistance)
- to cause high insulin levels that constrict coronary arteries
- to cause heart attacks.
Failure to respond to insulin causes:
- high blood sugar levels
- that cause sugar to stick to cell membranes
- to permanently damage the affected cell
- to cause blindness, deafness, heart attacks, strokes, amputations and all the terrible side effects of diabetes.
After just a few days on a high-calorie, high-fat diet, cells fail to respond adequately to insulin, blood sugar levels rise, fat deposits in your body, even in muscles, and you gain weight. This causes your muscles to start to lose their ability to store glycogen, the major source of efficient fuel for exercise, and you tire much earlier during exercise.
If you exercise vigorously BEFORE breakfast, you can reduce and even prevent these side effects. Exercising after fasting prevents fat from being deposited in muscles and helps muscles to make more stored sugar (glycogen), the primary efficient fuel for exercise.
A study from Leuven, Belgium shows for the first time that “fasted training is more potent than fed training to facilitate adaptations in muscles, and to improve whole-body glucose tolerance and insulin sensitivity” (Journal of Physiology, November 2010). So you are able to exercise longer and harder. If you do not exercise during this period, you gain none of these benefits. If you exercise after eating, these benefits are reduced markedly (Journal of Physiology, April 15, 2005).
When you exercise after fasting, you burn primarily your own body fat for energy. The fat is removed from fat cells and muscle cells. Muscle enzymes burn fat more efficiently and clear further fat from your muscles and fat cells to make your cells more sensitive to insulin. This reverses the cascade described in the first paragraph.
However, fasting before exercising harms training and competitive performance in athletes. The limiting factor to how fast you can move your muscles is the time it takes to move oxygen into muscles. When you fast before exercising, you burn more fat and less sugar. Since sugar requires less oxygen than fat to be converted to energy, your needs for oxygen are greater to burn fat. This slows you down and tires you earlier.
The basic research that showed how muscles convert sugar to energy was done in the 1930s by Diana’s father, professor Donald Purdie of Cambridge University in England. He worked with Hans Adolph Krebs, who won the Nobel Prize for Physiology or Medicine in 1953.
It is not established whether athletes should train on a low carbohydrate diet to teach their muscles to burn sugar more efficiently. This would help them to compete at a faster pace. Several studies show that training after fasting increases enzymes that turn sugar into energy. However, training with reduced sugar stores (glycogen) can limit workouts, and this may counteract the gains of fasting before working out.
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