Fasting Will Not Improve Endurance

Some athletes fast before competition because they think it will increase endurance.

Fasting before competition became popular because of an article in the Journal of Applied Physiology showing that rats can run further after fasting than after eating. How long you can exercise a muscle depends on how much sugar you can store in a muscle before you start to exercise.

Fasting prior to exercising uses up stored muscle sugar to make you tired earlier, but rats are different from people. In rats, fasting increased the rate that a rat's muscles use fat, to preserve stored muscle sugar. In humans, fasting does not cause muscles to burn more fat. After fasting, human muscles continue to burn primarily their own sugar. A study from Loma Linda shows that fasting for 24 hours uses up the same amount of muscle sugar as running for 90 minutes. Rats are different from people.

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2) Dohm J ApplPhysiol1986;61:1363-1368.

3) Pequignot J appl Physiol 1980;48:109-113.

Checked 8/9/08

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