Chronic lack of sleep could be one reason people are getting so broad in the beam, suggest the authors of two new studies.

Their research found that going without sleep seems to elevate blood levels of a key appetite-stimulating hormone, ghrelin. It causes levels of a “stop eating” hormone, known as leptin, to take a dive. The likely net effect is an increase in appetite.



“Sleep is not going to be the only answer, but we need to look into it,” says Dr Shahrad Taheri, a lecturer in medicine at the University of Bristol and author of one of the studies, published last week in the journal Public Library of Science Medicine.



Taheri says he has first-hand knowledge of the hunger-inducing powers of sleep deficits – the craving for salty, fatty food and the resulting extra heft that so many new doctors experience when going through their sleep-deprived medical residencies.



In the study conducted by Taheri and colleagues at Stanford University and the University of Wisconsin-Madison, the scientists examined data from 1,024 volunteers in a long-term sleep study. Analysing blood samples, the researchers found a clear pattern. Those who slept the least had the most ghrelin and least leptin, and those who slept the longest, vice versa.



The scientists also found that the subjects with the least sleep had a larger body mass index, a measure of whether someone’s overweight or not.



The other study, published last week in the Annals of Internal Medicine and conducted at the University of Chicago, artificially altered the sleep patterns of 12 healthy men. Each were given two days of restricted sleep (just four hours in bed) or extended sleep (ten hours in bed) on two occasions. All men consumed the same amount of calories during the sleep regimens, and blood samples were regularly drawn.



Again, the scientists found increases in ghrelin and decreases in leptin associated with sleep deprivation. They also found that the volunteers rated themselves as significantly hungrier – especially for high-calorie foods – when they had been deprived of sleep.



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