This is the result of an investigation, based on the analysis of brain activity using MRI, a group of volunteers, conducted by a team of experts from the University of California Berkeley, presented at the conference "Sleep 2012" at the Annual Meeting of the Associated Professional Sleep Societies.

The study, led by Stephanie Greer shows that sleep deprivation thwarts the decision areas of the frontal lobes that are no longer able to choose the right foods.

Another study presented in Boston, conducted a similar manner by Marie-Pierre St-Onge of Columbia University in New York, shows increased activity in brain areas related to desire and pleasure: that is, the more we sleep, our desire to turn the vision of unhealthy food.

Numerous studies have shown that short sleep tend to eat more, we prefer carbohydrates and fats, tend to gain weight. This is partly due to hormonal reasons as lack of sleep reduces the production of leptin, a hormone responsible for the decreased appetite by stimulating anorexigenic peptides.

However, these studies take into account the two halves of the story: they compared the brain's reaction to the volunteers at the sight of healthy foods and "junk food" when they had slept enough and when they had lack of sleep.

It has been shown that if we slept little and put us in front of "junk food" in the brain are activated more areas of less than razocinio desire and why we chose what we most want to eat. In practice, it is as if the lack of sleep make us succumb to the foods that harm us, because there is a reduction of our choice and also an increased desire for unhealthy food.