Getting 7-8 solid hours of sleep each night might seem an almost impossible luxury to many people. But not getting enough sleep is known to impair mental function and increase the risk for heart disease, among other ill effects. Accumulating evidence also suggests that even short-term, partial sleep deprivation could pave the way for weight gain and other negative metabolic consequences.
More than 28% of adults in the U.S. report that they get less than six hours of sleep a night, with this cumulative deprivation becoming more common in the past three decades. And now that more than 35 percent of U.S. adults are currently obese, researchers have been searching for potential links between the two conditions, in hopes of reducing the increasing health and economic burden of obesity. Establishing lack of sleep as a risk factor for weight gain could have important clinical and public health effects, possibly allowing people to make simple lifestyle changes to improve their metabolic health.
Poor sleep isn’t the only factor in weight gain, of course—there are several, including your genetics, your diet and exercise habits, your stress, and your health conditions. But the evidence is overwhelming: when sleep goes down, weight goes up.
Lacking sleep, you experience multiple changes to your body that can lead to weight gain. Sleep deprivation causes changes to hormones that regulate hunger and appetite. The hormone leptin suppresses appetite and encourages the body to expend energy. Sleep deprivation reduces leptin. The hormone ghrelin, on the other hand, triggers feelings of hunger—and ghrelin goes up when you’re short on sleep.
Sleep deprivation changes what foods you’re most interested in eating, creating more intense cravings for fat and sugar-laden foods. Low on sleep, your brain can’t make reasoned decisions and use its best judgment about food, and you’re more likely to be impulsive and give into junk-food desires. (More on the powerful effects of sleep deprivation on the brain soon.)
We also know that even after a moderate amount of sleep deprivation, you’re likely to eat more the next day. And lack of sleep makes you more likely to eat more of your overall calories at night, which can lead to weight gain.
Less sleep makes you look, and feel, older... and I don’t know anyone—man or woman—who wants to look and feel older than they are. Getting plenty of sleep is one way to help prevent that. I call sleep nature’s Botox—and here’s why:
During sleep—particularly during deep, slow-wave sleep, the body produces more human growth hormone, or HGH, and goes to work repairing and refreshing cells throughout the body—including cells of the skin, muscles, and bone. Short on sleep, you risk losing out on this important rejuvenation—and it’s going to show in how you look and feel.
Healthy, plentiful sleep is important to maintaining muscle mass—and sleep deprivation is linked to both reduced muscle mass and muscle strength in both men and women, particularly with age. Sleep deprivation also can interfere with bone health, reducing bone density and the production of new, strong bone.
Losing strength and mass in muscles and bones can affect everything from your posture to your flexibility to your ability to exercise and be active, to how well you heal after injury. To stay looking and feeling youthful, we need our muscles and bones strong and ready to work for us—and they need sleep to do that work.
Your risk for accident and injury goes through the roof. Whether you’re at home, on the job, on the sports field or behind the wheel, when sleep deprived you’re at much higher risk for accident and injury. I’ve written before about the dangers that not getting enough sleep poses to your safety, and research that shows how insomnia is a major risk factor for accidental death.
The effects on the brain from sleep deprivation are in many ways similar to the effects of drinking too much alcohol—yet drowsy driving still doesn’t get nearly the attention as drunk driving. Some of the latest research from AAA shows drivers who slept even 1 hour less than they typically do are at significantly higher risk for motor-vehicle crashes. And the more sleep deprivation piles on, the higher the crash risk goes. The study found drivers who slept less than 4 hours the night before had more than 11 times the crash rate as drivers who slept 7 or more hours a night.
You don’t heal as quickly from illness and injury when you don't get enough sleep.
There’s brand new research that suggests sleep is more important than nutrition to healing. The study is particularly interesting because the scientists set out to test how a nutritional boost might speed wound healing, even in the presence of sleep deprivation. Instead, they found it was sleep that really accelerated healing—and a lack of sleep slowed it down. This is consistent with other research showing that sleep deprivation slows the healing process.
Sleep has a powerful effect on the immune system, so it’s not just wound healing, but all forms of recovery from illness, injury, and disease that are affected by sleep. Your risks for coming down with an illness are greater when you’re sleep deprived, and it will take you longer to recover.
We’ve known for a while of the relationship between sleep and immune function. Both sleep and immune system activity are both regulated by circadian rhythms. And sleep—especially slow-wave sleep—is a time when the body’s immune activity goes into high gear, releasing more of its fighter cells, repairing damaged cells, and pushing back against disease. From the common cold to cancer, we’ve seen scientific evidence supporting sleep’s role in fighting illness.
If you’re sleep deprived, you not only weaken your immune system, but you also deprive yourself of the time when body naturally does some of its best work to heal and repair itself.
Remember, when you’re sleep deprived, you’re not just facing one of these issues: you’re more than likely grappling with all of them. Think about that the next time you’re tempted to shortchange your sleep because something else seems more important.