Here's why people want junk food when tired

London: Whenever we are tried, instead of opting for a healthier option such as a fruit, most of us prefer that favourite chocolate bar or packet of biscuits. Ever wondered why?

Researchers at Feinberg School of Medicine, Northwestern University in Chicago recently presented their results of a study looking into the effects of sleep deprivation upon high-calorific food consumption at the Cognitive Neuroscience Society's annual meeting in San Francisco, reports Science News.

Participants were allocated different amounts of sleep, eight hours or four hours, and then their reaction to smells of high-calorific foods were tested.

Participants slept for both lengths of time, separated by a week of normal sleep. On the day after they either had full or partial sleep, participants rated the pleasantness and intensity of sweet and savoury high-calorific food smells such as crisps and cinnamon rolls. They were then asked to rate the smell of non-foods like fir trees.

Researchers found that those who were sleep-deprived had "specifically enhanced" brain activity to the food smells compared to when they had a good night's sleep.

The experiment supports the long-held association between sleep deprivation and excessive eating and weight gain. So, if you want to stop reaching for the chocolate every day, perhaps a few extra hours sleep is all you need.