If you don't sleep well, you could well feel the pressing urge to gorge on junk food -- thus doing much harm to your health, says new research that seeks to shed light on the link between poor sleep and obesity. Researchers at the University of California, Berkeley, examined the brain regions that control food choices and found that inadequate sleep makes one crave junk food. "What we have discovered is that high-level brain regions required for complex judgements and decisions become blunted by a lack of sleep, while more primal brain structures that control motivation and desire are amplified," said Matthew Walker, a UC Berkeley professor of psychology and neuroscience and senior author of the study published Aug 6 in the journal Nature Communications. Moreover, he added: "High-calorie foods also became significantly more desirable when participants are sleep-deprived. This combination of altered brain activity and decision-making may help explain why people who sleep less also tend to be overweight or obese."