Why a Lack of Sleep Can Make You Fat, and How to Keep From Gaining Weight

by Lisa Fields

You stayed up too late last night, so you grab a latte on your way into work. When you feel yourself slump at 3 p.m., you raid the vending machine. You're so tired at the end of the day, you can barely get home for dinner, let alone make a trip to the gym.

Sound familiar? Many sleep-deprived people drag themselves through the day, skipping physical activity and relying on sugary pick-me-ups. But these habits don't fight off sleepiness for long. And even worse? Over time, they can contribute to weight gain or, at the very least, sabotage your efforts to lose those last few pounds. 

Lack of sleep changes your appetite
"We have very substantial research that shows if you shorten or disturb sleep, you increase your appetite for high-calorie dense foods," says Charles Samuels, MD, medical director of the Centre for Sleep and Human Performance in Calgary, Alberta. "On a simplistic level, your appetite changes."

Two hormones in your body play an important role in controlling appetite and satiety. Ghrelin stimulates appetite, causing you to eat; leptin suppresses appetite—so you'll stop eating—and stimulates energy expenditure. In a properly functioning brain, the two hormones are released on and off to regulate normal feelings of hunger. But research has shown that sleep deprivation can alter ghrelin and leptin levels.

"When sleep is restricted to four hours a night, ghrelin levels go up and leptin levels go down," says National Sleep Foundation spokesperson William Orr, PhD, president and CEO of the Lynn Health Science Institute in Oklahoma City. "So you have a greater amount of appetite and a greater amount of intake."

Belly fat raises your diabetes risk
If you're chronically sleep-deprived and consume more high-calorie foods, it's likely those calories will be deposited around your middle, forming fat deposits that are especially dangerous for raising your risk of type II diabetes. "It's known as visceral fat deposition," says Dr. Samuels. "Sleep-deprived individuals' ability to respond to a glucose load and release insulin is altered."

In one oft-cited study, he adds, healthy people whose sleep was restricted for six nights showed impaired glucose tolerance, which is a prediabetic condition. When they then got enough sleep, about nine hours a night over the next six nights, their glucose responses returned to normal.

There's not enough evidence to claim that lack of sleep could cause diabetes, but research has found a connection between the two. At the very least, getting enough sleep can help regulate energy levels—eliminating the need to rely on sugar or carbs for a boost—whether you have diabetes or not. 

If you sleep less, you may weigh more
Countering an occasional sleepless night with chocolate the next day won't set you back too far, but research suggests you may gain weight if sleep deprivation and overeating become routine. "Individuals who are obese tend to sleep less," says Orr. "There's been a marked increase in obesity over the last 10 years, and over the last 50 years, there's been a marked reduction in average sleep time for the average American—which suggests a link between sleep, appetite regulation, and obesity."

The trouble doesn't necessarily end if you watch what you eat. Cheat sleep and you may have more trouble losing weight, even if you have a healthy diet. If two women are the same age and weight, both eating healthy meals and walking five hours a week, but one isn't losing weight, "the first thing we'd ask is if she's getting enough sleep," says Dr. Samuels. "With weight control, we look at physical activity, movement, food intake, and recovery, and you have to focus on sleep and where it fits into this context. The fundamental foundation of recovery is sleep."

Kids and teens also may have problems if they skimp on sleep. Studies have shown that short sleep time in children and adolescents is associated with being overweight. One recent studyalso suggests a possible link between decreased REM sleep and an increased risk of being overweight.

Even if you're sleeping, you may not be sleeping well
"There are no guarantees that sleeping more will translate into pounds lost," says Orr. "But if you have chronic sleep deprivation or chronic fragmentation of sleep and you stop that habit or correct the problem so you sleep well, it will probably be easier to lose weight."

People with obstructive sleep apnea or other sleep fragmentation disorders experience these problems, even if they spend enough time in bed, because their sleep quality is poor and interrupted too frequently to reach deep, restorative levels. Since sleep disorders often cause extreme daytime fatigue, even the thought of exercise or physical activity can be daunting. Research has shown a connection between sleep apnea and obesity.

To fight sleep-deprivation-related weight gain and help make weight loss easier, try the following:

• Rest. "Get the sleep you need, end of story," says Dr. Samuels. "People always want some magic answer beyond that, but you've got to get your sleep. My biggest issue is people who wake up at 4 to go to the gym. People should focus on sleep first, to get to their goal from the weight perspective."
  
• Work out early in the day. "Exercise can aid sleep, but not right before bedtime," says American Dietetic Association spokesperson Jim White, RD, an American College of Sports Medicine–certified fitness instructor in Virginia Beach, Va. After working out, "adrenaline hormones and body temperature are up, which can keep you from falling asleep," he says.
  
• Eat right. "Protein is a critical factor for alertness, but people eat carbs when they're tired," says Dr. Samuels. "Instead, eat a handful of unsalted mixed nuts." Whole grains with fiber are also good, says White. "Sugary foods will give you an instant energy buzz for 30 to 45 minutes, but you'll see a big crash after that; whole grains will fuel you for a longer time."
  
• Avoid alcohol. Even if you think it relaxes you, don't turn to alcohol to calm down in the evening. "People don't realize that alcohol has nearly the same amount of calories per gram as fat," says Dr. Samuels. "When men stop drinking, boy, do they lose weight fast." Additionally, drinking alcohol close to bedtime can disrupt sleep: You may fall asleep more quickly after a few drinks, but you'll likely wake up more frequently during the night, and research indicates you'll get less REM sleep during the first half of the night.