I love sleep, but I’ve been getting far too little of it. My harried days have been stretching into late nights spent staring at the computer. And I’m not alone. The National Sleep Foundation estimates that the average American gets just 6.7 hours of sleep a night on weekdays.
We’re all familiar with the side effects of sleep deprivation — drowsiness, crankiness, an unnatural fixation with beds and pillows. But did you know that a lack of sleep can cause weight gain?
Anecdotally, this feels true. Late at night you can find me ransacking the cupboards for wayward cookies or stuffing myself with gummy bears. Staying up late makes me want to eat junk. And my unhealthy cravings continue into the next day. Tired and cranky, I make myself bacon or tater tots or peanut butter and Nutella sandwiches (shut up, they’re delicious).
The link between lack of sleep and weight gain is backed by honest-to-goodness scientific evidence too. In a study published last month, researchers tracked the sleeping patterns of 308 kids for a week. Those who got the least sleep tended to be the heaviest. Of course, a study like this can’t show whether the kids’ lack of sleep caused their obesity. But when you combine these results with findings from other studies (here, here, and here), the case becomes more compelling. I covered some of these studies in an article I wrote for Nature Medicine in 2008.
Two hormones, ghrelin and leptin, appear to play key roles. When your body needs food, your stomach releases the appetite-inducing hormone ghrelin. This ‘feed me’ signal makes its way to the hypothalamus — an almond-sized gland in the brain that controls, among other things, hunger and thirst. Meanwhile, fat cells send a competing message — the hormone leptin, which tells the hypothalamus that the body has ample energy reserves. Experimental studies suggest that sleep loss causes an increase in ghrelin levels and a decrease in leptin.
For people who are already heavy, lack of sleep may interfere with weight loss. In a study published last year, researchers recruited 10 overweight volunteers to participate in weight loss study. They split the participants into two groups. The first group got to sleep 8.5 hours a night. The second group was allowed to sleep just 5.5 hours a night. Although both groups received the same low-calorie diet, the group deprived of sleep lost less fat — just 1.3 lbs compared to 3 lbs in the normal sleepers. A clinical trial is now underway to test whether a year of longer sleep can help chronically sleep-deprived, obese individuals shed pounds.
While it’s unlikely an extra hour of shuteye will cure the global obesity epidemic, it may make us (and the people we come into contact with) happier.
The gummy bears are calling. But I’m going to resist. I have a dinner date with Mr. Sandman.
Image credit: Wikimedia Commons