Does sleep affect weight loss? How they are connected

In recent decades, the number of Americans with obesity has increased. At the same time, our average sleep duration has decreased. Coincidence? Researchers think not. 

When you are trying to lose weight, there are the obvious things that affect your progress: what you’re eating, how you’re staying active, and so on.

But then there are the less obvious factors, like how much sleep you’re getting. Sleep and weight loss are connected in ways that may surprise you. Read on as we explore how sleep affects weight loss.

In general, not getting enough sleep is associated with an increased risk of obesity and weight gain, as well as a higher body mass index (BMI). Research shows that even 5 days of too little sleep can lead to short-term weight gain. Poor sleep is linked with eating:

• A higher number of calories overall, often from fat, sugar, and carbohydrates

• More meals and snacks, especially at night

• More fast food

• Fewer fruits and veggies

Not only does sleep loss lead people to make less healthy food choices, but those foods in turn mess with your sleep, creating a vicious cycle. For example, eating more sugar and carbohydrates leads to more disrupted sleep. 

When you miss out on sleep, you have more hours in the day. Unfortunately, research consistently shows that we’re likely to spend those extra hours snacking or eating. And, since we don’t typically increase our activity levels when we’re sleep-deprived, those extra calories can transform into extra pounds. 

Even if you do manage to maintain a balance between your food intake and physical activity levels so that you lose weight (e.g. not overeating, or eating more but being more physically active as well), sleep deprivation still negatively affects weight loss in other ways, including body composition. Instead of losing weight from fat loss, you’re more likely to lose it from muscle and hold onto fat.

Several hormones are involved in regulating your appetite, but the two main ones are ghrelin (the “hunger” hormone) and leptin (the “fullness” hormone). Research has found that when you lose sleep, your leptin levels lower while ghrelin rises — leading to increased hunger and appetite. Over time, if poor sleep patterns become chronic, overeating may become a habit.

Sleep loss can also lead to insulin resistance, a hallmark of type 2 diabetes. According to a University of Chicago study, after just four days of sleep restriction, the body’s insulin sensitivity can plummet by 30%. Insulin sensitivity describes how well your body uses insulin to move glucose (sugar) from your bloodstream and transfer it to your cells, where it gets converted into energy. When you have lower insulin sensitivity, sugar gets trapped in the bloodstream where it causes damage to the nerves, blood vessels, and organs, and eventually, much of it gets stored as fat–– yet another example of how insufficient sleep poses an obstacle to weight loss. 

In a word, absolutely. Your brain finds food more appetizing when you’re sleep-deprived. Research shows that simply seeing images of food increases activity in your brain’s reward centers, compared with when you’ve had a good night’s sleep. People feel hungrier when they don’t get adequate sleep, and they’re more likely to reach for larger portions, snack more often, and eat less healthy foods.

Here’s how it works. When you’re sleep-deprived, working out can feel overwhelming, so you may skip your workout for the day. You’re too tired to cook at home, so you order fast food for takeout instead, which usually isn’t as healthy. On top of that, your hunger hormones are out of whack, so you’re more likely to reach for calorie-dense junk foods. 

Add to all of this the fact that your brain is tired. Sleep deprivation affects your decision-making and cognitive performance. When you’re tired, you’re more prone to make poor decisions, like deciding to forego your workout for the day or choosing a less-healthy meal. Not only that, but research suggests that it takes more effort for your brain to stay motivated when it’s sleep-deprived, so it’s even easier to brush aside your weight loss goals and grab an unhealthy snack.

Sleeping fewer than 6 hours per night is associated with increased snacking and more consumption of carbohydrates and sweets, particularly in the evening. In one study, participants were restricted to 4 hours of sleep per night. These poor sleep-deprived individuals consumed an average of 550 extra calories before their delayed bedtimes. Their late-night snacks were more likely to have a high-fat content. By the end of the study, these participants had gained significantly more weight than the control group.

The thing is, our bodies aren’t built to digest all that food late at night. Because we are diurnal animals, our circadian rhythms are wired for activity during the day and rest at night. As a result, our metabolism is slower at night. So, you may burn fewer calories from late-night snacks vs. meals you eat earlier in the day.

Many factors are involved in weight loss, including your diet, level of physical activity, existing health conditions, genetics, and more. A reduced-calorie diet and increased exercise are typically the first two recommendations for people trying to lose weight. But, a growing body of research suggests that sleep may be another factor in how smoothly your weight loss journey goes. 

Insufficient sleep may make you less likely to stick to your exercise routine, which can stymie weight loss efforts. Sleep-deprived people tend to increase their calorie intake and snack more often — but they don’t necessarily use more energy. Instead, they maintain the same level of energy expenditure, upsetting the balance of calories consumed vs. calories burned required for weight loss.

Sleep may also play a key role in weight maintenance, which is itself an important piece of the weight loss puzzle. In a study of men who had lost at least 10% of their body weight, those who slept longer were more likely to keep off more weight, despite being less likely to follow a vigorous workout routine.

This isn’t to say that exercise isn’t important. Exercise offers a host of health benefits beyond weight loss. And, exercise can help you sleep longer and deeper. Plus, regular physical activity during the day helps reinforce your circadian rhythms, further contributing to healthy sleep.

Yes, you do actually burn calories during sleep, although your metabolism works much more slowly than when you are awake or active. During each hour of sleep, a person may burn 40–50 calories, give or take, depending on their body weight. For comparison, reading while sitting for an hour may burn 70–90 calories, while an hour of dancing can burn 330–470 calories.

A lack of sleep is no friend to weight loss. However, sleeping longer, and sleeping better, are both associated with more successful weight loss. Developing good sleep habits can make it easier to achieve and maintain a healthy weight. Get started with these tips for good sleep:

• Make time to sleep. Experts recommend 7–9 hours per night of shuteye per night for adults. Do what you can to make room for a bit more sleep, even if that means saying no to binge-watching your favorite TV show.

• Follow a sleep schedule. If it helps, schedule sleep on your calendar. Aim to get the same amount of sleep every night. Trying to make up for short sleep on the weekends can backfire. While you may eat less at night on those weekend days where you get enough sleep, your fatigue will return on the weekdays, disrupting your circadian rhythm and leading to increased post-dinner caloric intake, body weight, and cravings.

• Save your bedroom for sleep and sex only. Reserving your bedroom for activities associated with relaxation helps your brain recognize it as a place where you rest and relax. Avoid working (or working out) in your bedroom. Remove any items that remind you of anything stressful, too, such as your work laptop. 

• Don’t eat too late. Eating late at night can mess with your digestion, disrupting the restfulness of your sleep. Plus, some research suggests that eating other meals later in the day, such as skipping breakfast or eating a late lunch, may lead to slower weight loss. 

• Create a relaxing bedtime ritual. Get in the mood for sleep by dedicating the last 30–60 minutes of the night to winding down. Dim the lights, light an aromatherapy candle, and turn off your electronics (even your phone!). Instead, occupy your mind with a low-key activity like knitting, drawing, or meditation.

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Current version

July 26, 2023

Written by

Amelia Willson

Fact checked by

Yael Cooperman, MD

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About the medical reviewer

Yael Cooperman, MD, Ro

Yael Cooperman is a physician and works as a Senior Manager, Medical Content & Education at Ro.