Willpower is finite like muscle strength and can be worn down through excessive use or replenished through eating or sleeping, research has shown. Mental energy is thought to be comparable to physical energy, and using self-control depletes mental energy in the same way that exercise does to the body. Eating might help increase willpower because it provides the brain with glucose, the simple sugar that gives the body energy. Sleeping also might improve willpower, because sleep deprivation has been found to affect the function of the prefrontal cortex, the part of the brain responsible for making decisions, which might result in a higher likelihood of giving into temptation.
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