Most of us know, all too well, that losing even a little bit of sleep can sap us of energy and make us feel far less productive in all that we do. But emerging research suggests that too little sleep may also affect the food choices we make and how much we eat and potentially contribute to excess intake and eventual obesity.
Although researchers are still trying to figure out how inadequate sleep relates to food preferences and eating habits, some lab studies have found that shorter sleep was associated with greater hunger--especially for high-fat, high-carbohydrate foods--lower levels of leptin (a feel-full hormone), and higher levels of ghrelin (the hunger hormone).
Two new studies shed a little light on how sleep duration and the timing of sleep affect nutrient intake and dietary patterns. In a study published last month in Appetite, researchers from the University of Pennsylvania and the University of Chicago evaluated the associations between habitual sleep duration and nutrient intake in a sample of 5,587 adults aged 18 and older who participated in the 2007-2008 National Health and Nutrition Examination Survey (NHANES). Adults were classified as one of the following:
-- very short sleepers, who averaged less than five hours of sleep a night;
-- short sleepers, who averaged five to six hours of sleep a night;
-- typical sleepers, who averaged seven to eight hours of sleep a night; or
-- long sleepers, who averaged at least nine hours of sleep a night.
While very short sleepers had the lowest overall calorie intake, short sleepers consumed slightly more calories than typical sleepers. Compared to typical sleepers, short, very short, and long sleepers had less variety in their diets.
Researchers also found that very short sleepers consumed less lycopene, a plant chemical that may protect against cancer and that acts as an antioxidant to protect against cell damage caused by free radicals. Short sleepers also consumed less vitamin C and selenium, two key antioxidant nutrients, and lutein and zeaxanthin, plant chemicals that may reduce the risk of age-related macular degeneration, a leading cause of blindness.
In another study published last month in Appetite, researchers assessed how the timing of sleep affected dietary patterns in 52 male and female adults who were classified as either:
-- normal sleepers, for whom the midpoint of their sleep was before 5:30 a.m., or
-- late sleepers, for whom the midpoint of their sleep was at or after 5:30 a.m.
Researchers found that, over seven days, late sleepers consumed an average of 248 more calories per day than normal sleepers; the majority of those extra calories were consumed at, and after, dinner. Late sleepers also reported higher caloric intake at dinner and after 8 p.m. They also found that late sleepers made more poor food choices than normal sleepers--for example, they ate twice the fast food, twice the full-calorie sodas, and about half the servings of fruits and vegetables as normal sleepers. The researchers concluded that the increased calorie intake of late sleepers could contribute to a 2-pound-per-month weight gain unless physical activity was increased to compensate.
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So, what's the bottom line when it comes to sleep and diet?
According to Michael Grandner, a University of Pennsylvania sleep researcher (and lead researcher of the first Appetite study mentioned earlier), "We have long suspected that sleep and diet were related--we just didn't know what that relationship would look like. And although we are still figuring out whether specific nutrients can alter your sleep, we now have some good evidence that a healthy diet supports healthy sleep."
Of course, setting yourself up for a good night's sleep by sticking to a regular sleeping schedule, darkening your room, and limiting electronics and other stimulation close to bedtime is a good line of defense against eating too much (and grabbing one too many nutrient-poor comfort foods).
But, for those inevitable times when you don't sleep well or enough--when your child wakes up sick, when you're out late at an event, when you travel, or when you have to burn the midnight oil to make an important deadline--registered dietitian Marjorie Nolan Cohn, a spokesperson for the Academy of Nutrition and Dietetics, suggests four strategies to ensure you don't go overboard on your calories:
1. Eat on the Clock. Nolan Cohn says that aiming for three meals and one snack, spaced every three to four hours, can help your body stay in sync with the natural peaks of the hunger hormone, ghrelin. "Eating this way can help you successfully avoid hunger and mindless noshing throughout the day," she says.
2. Go Pro. According to Nolan Cohn, "Ghrelin plays an important role in blood sugar regulation, and when ghrelin is out of whack from losing sleep, your blood sugar is at risk of dropping throughout the day. This leaves you susceptible to hunger and sugar cravings." To suppress ghrelin levels and keep blood sugar levels steady, Nolan Cohn suggests including some lean animal protein, such as chicken breast, fish, 95 percent lean beef, or egg whites, at meals.
3. Take a rest. When your body and mind are overly tired, 10 minutes of rest may be just enough to reset your ghrelin sensors to prevent high levels that set you up to overeat, says Nolan Cohn. "Taking even 10 minutes to dim the lights, put your feet up, and close your eyes may do the trick," she says.
4. Resist. Although cardiovascular exercise is necessary to strengthen the heart and boost overall health, Nolan Cohn says it burns a lot of calories, driving up ghrelin levels. On the other hand, resistance training doesn't burn a lot of calories in the short term and, therefore, doesn't affect ghrelin levels.
"Resistance training also has the added benefit of building muscle, which boosts overall metabolic rate--critical for long-term weight management," she says. So when you're tired, it might be a good idea to grab some weights, or do some push ups rather than always go for a cardio workout. An added bonus? The extra muscle mass you'll gain over time will keep your metabolism revved up.
Thanks to Stefani Pappas for research and assistance.
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Elisa Zied, MS, RD, CDN, is the founder and president of Zied Health Communications, LLC, based in New York City. She's an award-winning registered dietitian and author of three books including Nutrition At Your Fingertips. A graduate of the University of Pennsylvania and New York University, Zied inspires others to make more healthful food choices and find enjoyable ways to "move it or lose it" through writing, public speaking, and media appearances. You can connect with her on twitter (@elisazied) and through her new Stressipes forum on her website: www.elisazied.com.