It has long been known that sleep deprivation seems to compel people to eat more food—and often food that is not very good for you—the next day. But until now nobody has looked into the reason why. The theory which inspired this research suggests that these cravings could be the result of the way sleep deprivation alters appetite hormones or if sleep deprivation actually changes the circuitry in the brain.
To learn more about this and attempt to answer these questions, then, researchers from the University of Cologne, in Germany, took 32 healthy men and conducted two identical series of experiments. For both sets, these men were tested first thing in the morning on their desire for snack foods while also observing brain activity and hormone levels. Both sets also had dinner—in a laboratory—the night before, which would indicate their final meal before the testing phase of the experiment.
The testing environment, then, comes in the form of sleep deprivation. For one night, these men would be sent home after dinner so they could have a normal sleep cycle in a familiar environment. The second night, though, these men were kept in the lab after dinner and forced to stay awake the rest of the night.
For each of the two sets in the series, each man was then given some money the following morning, about enough to buy a few “trinkets:” about the equivalent of a few dollars. This money was to be spent specifically on a range of snacks. In addition, the researchers scanned the subjects’ brains with functional magnetic resonance imaging (fMRI) to observe them making decisions about how much they would be willing to pay for each of the provided items. Each man, then, would be able to bid on these items in a computer auction (and were also allowed to eat their chosen snack if they purchased it).
On the mornings following the sleepless night, these men increased the value they were willing to pay for snack foods despite the presence of the same items and despite the men reporting the same feelings of morning hunger. The fMRI scans, however, also showed higher activity in the amygdala and the hypothalamus, regions of the brain which are associated to hunger and decision-making.
More important, they did not find a correlation between hormone levels and value response after sleep deprivation. This leads to the conclusion that overeating after sleep loss is more pleasure based than hormonal.
The result of this study has been published in the Journal of Neuroscience