The less we sleep, the more we’ll weigh - that’s what the observational evidence seems to indicate, and some randomized controlled studies have backed this up. But what causes these weight changes at the biological level? Recent research into the sleep-deprived brain has started to answer this question.
One clue comes from brain scans of sleep-deprived subjects, which have shown increased activity in response to food in areas of the brain involved with reward, such as the putamen, insula, and nucleus accumbens. Another brain area, the anterior cingulate cortex (ACC), showed increased activity in subjects who were totally deprived of sleep when shown pictures of food, and the activity correlated to how desirable they found the food to be. It seems these brain regions respond more strongly to food when sleep-deprived.
It also turns out that similar regions of the brain also respond to food abnormally in obese people. For instance, one study found increased activation in the ACC, putamen, and insula as well as other brain regions in response to pictures of high-calorie foods in obese people, compared to normal-weight individuals. And the sum of recent evidence suggests that there are differences in the brain activity of obese and normal-weight people.
Many of the brain regions that activate more strongly in response to food stimuli in sleep-deprived and obese people have something in common: they are part of what’s known as the “salience network”. The role of the salience network is to take stock of how the body is doing as a whole, and guide behavior to make things better if something is amiss. It’s the system that draws attention to something that might be useful in your environment, generates some of the impulse to act, and doles out a reward when what was desired is obtained. Could sleep deprivation activate the salience network and make food, or at least certain kinds of food, more palatable? That’s what this study intended to explore.
There’s a wealth of evidence to suggest that sleep deprivation is associated with obesity. Parts of the brain, like the anterior cingulate cortex (ACC), putamen, and insula over-activate in response to food stimuli in both obese and sleep-deprived people. These parts of the brain are known as the “salience network,” which notices things in the environment and drives action to obtain them as needed. This study explored how the salience network was associated with food intake after sleep deprivation.