Does Your Body Burn Fat When You Exercise on an Empty Stomach?

Weight loss is one of the many benefits of exercise, but there are many conflicting opinions regarding how to achieve optimum results. A point of contention among both researchers and exercisers is whether or not the body burns more fat when you exercise on an empty stomach. There is evidence both for and against this theory. Some exercisers may find that exercising on an empty stomach works for them while for others it may be extremely difficult. Always consult your doctor before beginning any exercise routine.


The theory behind this practice, according to Maria Cheng of MSNBC Fitness, is that exercising after skipping breakfast leaves your body in a fasting state. This deprives your body of carbohydrates, which are its primary source of fuel, and forces it to burn stored fat instead. Exercising while fasting also results in low levels of insulin and high levels of adrenaline, which increases the amount of fat burned.

Supporting Evidence

Jacquelyn Rudis of the Beth Israel Deaconess Medical Center says that a study published in the "International Journal of Sports Medicine" supports this theory. The researchers compared the fat metabolism of eight female subjects in four separate trials. The last trial required them to exercise on an empty stomach. The results showed that the women burned more fat while fasting.

Opposing Research

A study published in the "International Journal of Sport Nutrition and Exercise Metabolism" provided an opposing view. Though exercising while fasting does burn more calories from fat, the researchers found that performance was improved by a light meal three hours before the exercise. A high-carbohydrate, low-protein, low-fat meal is recommended.

Warnings and Considerations

This method does not work for everyone. You should not lift weights while fasting because strength training puts large amounts of stress on the muscles and requires proper fuel. The muscles will not be worked effectively if you exercise without eating first. Exercising on an empty stomach may also cause dizziness and fatigue, which will reduce the time and quality of your workout. This practice may also cause the body to metabolize muscle for fuel if the workout lasts more than 30 minutes. Exercising on an empty stomach also lowers your blood pressure and causes extreme hunger, which may cause you to make poor dietary choices later.