There’s now a scientific reason behind those late night cravings for pizza or chips and dip. In a new report, scientists have discovered that when people are sleep deprived they are drawn toward high calorie and high fat foods, Aicube reports. A sleep deprived brain associates junk food with reward and pleasure, unlike a well rested brain, which does not. The reward perception alters when a person has too little sleep.

The study, conducted by Marie-Pierre St-Ong and others at Columbia University, tracked twenty-five people of average weight and scanned their brains using functional magnetic resonance imaging technology. The scan tracked the blood in the volunteers’ brains while they looked at healthy food versus junk food. And what those scans found was illuminating for many people who are fighting the near constant battle to control their weight.

The brains of people who were operating on nine hours sleep for five days weren’t influenced by the unhealthy food. However, the reward center of the brain of people who had only slept four hours a night for five days, lit up when they saw high calorie items such as cake and cookies.

What the study clearly showed is that people who don’t get enough sleep are sorely tempted by fatty foods. And that is a problem for maintaining a healthy weight because when a person eats junk food late at night they don’t have a chance to burn off the calories.

So what is the reason a person would be more tempted to eat poorly when tired? The answer is in our DNA. When the body is exhausted, it craves high calorie foods for fast energy. Because a person is susceptible to indulging in high calorie foods when tired, that means they should offer themselves many other options. Snacks like fruit or celery with low-fat cream cheese can help keep the temptation for sweet and savory treats at bay.

However, the most important thing is to get enough sleep. Not only does sleep deprivation make a person weak-willed around junk food, it’s also dangerous for driving and work place safety. Everyone should try to get at least 7 hours of sleep a night, if not more.