The United States is in the midst of an obesity epidemic: Nearly three-fourths (71 percent) of Americans age 20 and over are overweight or obese, according to the Centers for Disease Control and Prevention (CDC).
We’re also experiencing what some call a “sleep deprivation epidemic.” Data from the CDC’s Behavioral Risk Factor Surveillance System showed that for this same age group, 35 percent reported getting fewer than seven hours of sleep during a typical 24-hour period, 48 percent reported snoring (a sign that could indicate a sleep disorder called sleep apnea), 38 percent reported unintentionally falling asleep during the day at least once in the preceding month, and 5 percent said they nodded off or fell asleep while driving at least once in the preceding month.
Research has also shown that people who rarely get enough sleep are more likely to add on extra pounds than those who are well rested. Here’s a look at the connection.
What the science says
Dozens of studies have connected lack of sleep to weight gain. For example, a study that was published in the journal Sleep Medicine in 2014 followed 1,145 people for 11 years and found that the odds of becoming obese over time were significantly higher in people who slept seven or fewer hours each night.
Findings from a small study of 16 healthy adults, published in PNAS (Proceedings of the National Academy of Sciences), found that people who failed to get enough sleep for just one week gained on average about 2 pounds during that brief period of time.
The investigators reported that overall, when the study participants got too little sleep, they consumed more calories than they did when they got a sufficient amount of sleep.
Why does it happen?
The explanation for the link between sleep loss and weight gain is based on several major theories.
• Hormones. Researchers have found that sleep restriction lowers levels of leptin, the hormone that signals satiety. When leptin is low, your brain receives the message that you should eat more, even if your body doesn’t need more calories.
At the same time, sleep restriction increases levels of the hormone ghrelin, which promotes appetite. This hormonal double-punch not only makes you feel hungrier, but also prevents you from feeling sated after eating.
Cortisol—a hormone that is released in response to stressful situations, such as not getting enough sleep—may also increase appetite. And levels of the neuropeptide (small hormone produced in the brain) orexin, which can increase food cravings and consumption of high-fat foods, also go up in individuals who don’t get enough sleep.
• Insulin resistance. Sleep deprivation appears to make the body more resistant to insulin and interrupt healthy glucose metabolism. In response to the insulin resistance, the pancreas releases extra insulin into the bloodstream.
Insulin resistance and extra insulin production can compromise beta-cell function and lead to type 2 diabetes; this combination also promotes the deposition of triglycerides into fat cells, which causes weight gain.
A small 2012 study in the Annals of Internal Medicine showed that after just four nights of restricted sleep (reduced from 8.5 hours to 4.5 hours), the participants’ fat cells became insulin-resistant.
• Lifestyle. Being tired can also make it hard to maintain healthy lifestyle habits. Fatigue can be a big obstacle to exercise—after all, who feels like going to the gym when exhausted?
It can also play tricks on your mind: People often confuse the feelings of tiredness with hunger, sending them to the kitchen for a snack rather than to the bedroom for a nap. What’s more, sleeping less means more time for eating.
Weight also affects sleep
Evidence suggests that being overweight or obese makes it harder to get a good night’s sleep. Overweight people are at greater risk of developing sleep apnea, which afflicts some 18 million Americans.
Weight gain—especially in the trunk and neck area—can increase the risk of sleep apnea by compromising respiratory function. People with sleep apnea actually stop breathing during sleep, sometimes hundreds of times a night. When breathing stops, the brain must arouse the person slightly in order to jump-start respiration.
This constant, slight waking up can lead to fragmented, unsatisfying sleep and daytime fatigue, a vicious circle of poor sleep and weight gain that reinforces itself. Excess weight also leads to such conditions as arthritis, diabetes, and heart disease, each of which can affect your ability to get a good night’s rest.
How much do you need?
While most individuals find that they function best on the recommended seven or eight hours of sleep every night, you may need more or less sleep to feel completely rested. Try to get the amount that leaves you feeling alert and refreshed.
If you find that you have trouble falling or staying asleep, talk to your doctor about possible solutions. And if you have to skimp on sleep during the week, attempt to make it up by sleeping longer on the weekend—though there is still no real substitute for getting a full night’s sleep on a daily basis.
Learn more about possible sleep aids, including pyschotherapy and melatonin.