A lack of sleep can make you more likely to reach for chocolate, ice cream, and other high-calorie foods, and now researchers have more understanding why: Your fat cells don't function as well when they haven't gotten enough zzzs.
Much like your brain needs sleep for cognitive function and memory consolidation, your fat cells need similar type rest, says Matthew Brady, Ph.D., associate professor of medicine at the Kovler Diabetes Center at the University of Chicago.
"Just as you can have groggy thinking with too little sleep, you fat cells also get metabolically groggy," he says. "They don't respond as well to insulin and don't function as well as with a full-night sleep."
And when it comes to maintaining a healthy weight, insulin is king in both the short- and long-term.
Brady says that short-term, insulin-promoted glucose metabolism drives the production of the hormone leptin from fat to the brain, which decreases your hunger drive.
"It has previously been shown that sleep deprivation decreases circulating leptin levels, and the participants in our study were hungrier. Thus sleep deprivation can promote overeating and weight gain," Brady says.
In the long run, decreased insulin sensitivity can lead to serious health problems. Your fat cells safely store lipids inside, but when they become insulin-resistant, the stored lipids leach out in the bloodstream and can accumulate in other tissues (which could lead to fatty liver) and induce systemic insulin resistance, the first step toward developing type 2 diabetes.
In the study, just four nights of 4.5 hours of sleep reduced insulin sensitivity in fat cells by 30 percent in lean, healthy young participants. The perfect amount of sleep is unknown, but Brady recommends getting as close to eight hours a night as you can.
Jennipher Walters is the CEO and co-founder of the healthy living websites FitBottomedGirls.com and FitBottomedMamas.com. A certified personal trainer, lifestyle and weight management coach and group exercise instructor, she also holds an MA in health journalism and regularly writes about all things fitness and wellness for various online publications.