Now that 2013 is in full swing, some of us may have lost sight of those New Year’s resolutions we made to eat right and get a good night’s sleep. Perhaps things have gotten busy at work or at school – we just don’t have the time to cook those well-balanced meals or to make it to bed at a reasonable hour. As most of us can attest, not getting enough sleep makes all of life’s daily tasks seem harder to juggle. What you may not have known, however, is that sleepiness can undermine your goals to eat right.
In a paper recently published in the journal NeuroImage, a group of researchers at Harvard Medical School report their investigation into the relation between sleep and overeating. They began by inviting thirty-eight healthy adults to have their brains scanned using fMRI. While in the scanner, the researchers showed the volunteers pictures of both healthy foods (fresh salads, fruits, vegetables, fresh fish, whole grain bread) and unhealthy ones (cheeseburgers, French fries, cake, ice cream, candy). They also asked folks a series of questions designed to capture how sleepy, on average, they tended to be during the day, how large their appetite usually was, and how often they tended to overeat – eating more than they set out to eat.
Here’s what the researchers found: The more sleepy people tended to be during the day, the less activity they showed in the ventral-medial prefrontal cortex (vmPFC) when viewing the high-calorie as opposed to the low-calorie, healthier foods. Why is this interesting? The vmPFC is an area of the brain that has been implicated in our ability to inhibit and control our emotions and behavior. Less activity in this brain area when viewing unhealthy (relative to healthy) foods may reflect the fact that people don’t have the brainpower needed to control their impulses. But, that’s not all. The researchers also found that the operation of the vmPFC also predicted people’s tendency to overeat during meals – with less activation related to more overeating. The take home? Sleepiness may lead to overeating because prefrontal brain regions important for reigning in our impulses don’t work as well when we are tired.
One interesting caveat to these findings is that the researchers found that prefrontal brain activity predicted women’s but not men’s tendency to overeat. This sex difference emerged even though the men and the women in the study had similar overall sleep patterns, appetites, and had consumed roughly the same amount of calories the day of the fMRI scan.
Though the jury is still out as to why the sex difference occurred, this work contributes to a growing consensus that a lack of adequate sleep can lead to poor eating habits, weight gain and even obesity. Indeed, in the last several decades, there has been a frightening increase in weight gain in the U.S. coupled with a decrease in the amount and quality of sleep Americans get. This new research suggests that not getting enough sleep may do a lot more than just lead to feelings of sleepiness during the day. Sleepiness may affect the functioning of brain regions important for regulating our food intake.
For more on why we sometimes fail to keep our thoughts and impulses in check, take a look at my book Choke!
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Killgore, W.D.S, et al. (in press). Daytime Sleepiness Affects Prefrontal Regulation of Food Intake. NeuroImage.