Back in the late 1980s and early 1990s, when I was new to lifting and the bodybuilding scene, we didn’t think of sleep as a helpful tool for getting in shape. Why would you lie in bed snoring when you could be up and about, burning calories, and getting things done?
I’m not sure how fitness athletes view sleep these days, but social media tells me there are a lot of early mornings and late nights. Almost as if getting by with as little sleep as possible has some intrinsic value. However, now we have plenty of research showing that sleep does not prevent you from getting shredded. On the contrary, getting plenty of sleep helps you lose fat and get in shape.
In this article, I dissect a new study that furthers the notion of sleep being one of the best things for you if you’re looking to lose weight, shed body fat, and get in shape.
How Sleep and the Lack of It Affects Your Body
Sleep requirements vary from person to person, but most need 7–9 hours per night to function optimally.1 Getting too little sleep can be detrimental to your health and is associated with several medical issues, including diabetes and heart disease.2 Many sleep fewer than the recommended number of hours, though. For example, according to CDC data, a third of US adults regularly sleep fewer than seven hours per night.3 I bet that many sleep a lot less than that.
Not getting enough sleep is also a significant risk factor for obesity. According to epidemiological studies and compared to sleeping seven hours per night, each hour of sleep deprivation increases the risk of obesity by 9%.4
Research shows that people increase their energy intake by up to 350 calories per day when they don’t get enough sleep. That kind of overeating would mean gaining 15 kilograms (33 lb.) in a year. That’s not something you see in a real-life scenario just from not sleeping enough, though. Short-term studies with huge sleep deficits looking at just a meal or two don’t provide the complete picture. While it’s true that sleeping too little increases the risk of obesity, it doesn’t pack on the pounds like that.
That being said, getting too little sleep is detrimental to weight control and your body composition.
- You feel hungrier and eat more. You’re also more likely to reach for unhealthy snacks packed with calories rather than sitting down for a nutritious meal.
In summary, sleep is your friend, both when you’re looking to build muscle and when you’re trying to lose fat and get shredded or just a little less rotund. And that leads us to the new study I mentioned earlier.7
New Research: Sleep More, Eat Less
If you’ve read this far, you know that sleep deprivation is associated with eating more calories. Not getting enough sleep means an increased risk of overeating and making less healthy food choices. The new study asks the opposite question: does sleeping more make you eat less? Participants not meeting general sleep recommendations were coached to sleep more, and the researchers tracked their food intake to see if the intervention affected their calorie intake.
The researchers recruited 41 men and 39 women between 21 and 40, all overweight with a BMI between 25 and 29.9. All of them habitually slept 6.5 hours or less per night for at least six months before the study. The researchers randomized the subjects into one sleep extension group assigned to individualized sleep hygiene counseling and one control group that maintained their usual sleeping habits.
Before the sleep intervention part of the study started, the researchers made sure the participants didn’t sleep more than 6.5 hours per night by letting them wear an actigraph unit (a gadget you wear on your wrist and which monitors your rest/activity cycles) for a week. They also eliminated potential participants with medical issues like sleep apnea, clinical insomnia, or a history of sleeping disorders. They looked for subjects who habitually curtailed their sleep duration but not for medical reasons. Also, people working the night shift or with rotating shift work were out as those affect sleeping patterns.
The participants were blinded to the purpose of the study. The researchers described the study in vague terms as a collection of “information about sleep habits and metabolism.” That way, they could monitor the participants’ sleep patterns without influencing their everyday (or everynight, perhaps) habits. It was also a way to avoid applications from people who only wanted to participate in the study to improve their sleep habits.
The study lasted four weeks. During the first two weeks, the researchers gathered data on the participants’ sleep habits. They wore accelerometers tracking their motion and pushed a button when they went to bed and another when they crawled out of bed in the morning. With the help of a validated algorithm, the researchers calculated how much of that time the participants spent sleeping.
On the morning of day 15, the 80 men and women were randomized into two groups: a control group who continued with their lives as usual and a sleep extension group who would sleep more than usual the upcoming two weeks. The participants of the sleep group received individualized sleep hygiene counseling intending to increase sleep duration by two hours per night. After a week, on day 22, the researchers provided additional sleep counseling if needed.
Calories In, Calories Out, Body Weight, and Body Composition
The participant’s diet was not controlled in any way, but the researchers were able to calculate their calorie intake without locking them up in a lab.
They used the so-called doubly labeled water method to track the participants’ total energy expenditure. That means labeling water with isotopes that let you track how many calories someone burns after drinking it. You then measure how much of the isotopes remain after a specific time, up to two weeks, which lets you calculate the metabolic rate of the person who drank the water.
The researchers also tracked the participants’ resting metabolic rate using indirect calorimetry, both fasted and following a meal. Indirect calorimetry is a method where you use a respirometer to analyze the amount of oxygen you breathe in and out, letting you calculate how many calories you expend.
In addition, they also calculated the thermic effect of feeding in every participant, meaning how many calories it takes for your body to digest and metabolize the food you eat.
Whew! That’s a lot of measuring and calculating. Precise calculations, too. As accurate as you get without locking the participants up in a sealed chamber for the study duration.
With the help of the gathered information, the researchers could calculate how many calories the participants ate. They looked at how their body weight and composition, as measured using DEXA-scans, changed over time. Body fat and fat-free mass contain different amounts of energy. By comparing energy expenditure with changes in body weight and body composition, the researchers found out the participants’ calorie intake without directly controlling their diet.
Results: Sleep and Calorie Intake
The sleep hygiene counseling the sleep extension group received paid off. The graph below shows the sleep pattern of both the control and the sleep groups.
As you can see, the sleep extension group began sleeping significantly more after the intervention, while the control group kept sleeping fewer than 6.5 hours per night.
When they increased their sleep duration, the participants in the sleep extension group began eating less. On average, they ate 270 calories less per day. Every extra hour of sleep was associated with a decrease in calorie intake of approximately 162 calories per day. On the other hand, the control group increased their calories slightly throughout the study.
Neither of the groups saw changes in how many calories they burned. They all went on with their lives as usual, and sleeping more didn’t make the sleep intervention group burn more or fewer calories. However, they did sleep a couple of hours extra, burning fewer calories during that time, which might have meant they became a little more physically active during waking hours. Despite spending more time in bed, they didn’t burn fewer calories in total, suggesting that they increased their energy expenditure when they were up and about. Perhaps they moved around more without thinking about it, which would be another positive effect. But that’s pure speculation on my part.
Despite the study only lasting a few weeks, the sleep extension group lost almost a kilogram of body weight. That kilogram mainly was water weight, which is common during initial weight loss. According to the researchers, if sleep is extended over extended periods, weight loss in fat would likely increase over time. That’s what usually happens when you lose weight: at first, you see a rapid loss of water weight, which turns into actual fat- and muscle loss after a week or two. You don’t have to worry about losing muscle if you lift weights, though!
The control group gained a small amount of weight throughout the study.
The sex of the participants did not affect the results, and neither did menstrual cycles.
This study was well-designed and with quite a large number of participants. It demonstrated that overweight men and women who slept less than the recommended amount ate fewer calories when they upped their sleep duration. It is also the first study showing that normal but sleep-deprived adults in real-life scenarios spontaneously reduce their food intake and lose a pound or two of body weight if they fix their sleep habits.
- On average, the participants in the sleep extension group ate 270 calories less per day. The study only lasted a couple of weeks, but if the effects continue, they predict a weight loss of 12 kilograms (26.5 lb.) after three years, as seen in previous research.
- The participants who received sleep hygiene counseling added an average of 72 minutes of sleep per night. Some nights they slept more, others less, just like most of us.
- Compared to the control group, the subjects in the sleep extension group felt more energetic and alert, as well as experiencing a better mood overall.
Conclusion: Sleep More, Eat Less
We already know that not getting enough sleep is associated with health issues and makes losing weight and body fat more challenging. This study suggests benefits of sleeping more if you’re not getting the recommended seven hours of Zs per night. Not only do you decrease the risk of various medical issues, but you also make it easier to lose weight by eating fewer calories without even thinking about it.
Of course, it can be easier said than done to add hours of sleep just like that. If you’re having trouble sleeping because of medical reasons or if you are surrounded by disturbances beyond your control, like a small child or two, you simply have to make the best of your situation. That means exercising. This study had nothing to do with strength training, but plenty of research shows that physical activity and exercise, including strength training, are great if you have sleep issues. Not only does exercise make it easier to fall asleep, it counteracts many of the health issues associated with sleep deprivation. And if you’re on a weight-loss diet, strength training ensures you’re losing fat, not muscle, even if you’re not getting optimal amounts of sleep.
Many of us have the opportunity to change our sleep habits, though. It’s likely worth giving up an hour or two in front of the tv or some other time-consuming and non-essential activity to get more quality time in bed. It’ll make you feel more energetic, improve your health, and make it easier to control your body weight and body composition, even without counting a single calorie.
- The Effect of Napping on Performance
- 5 Reasons You’re Not Gaining Muscle
- Building Muscle and Losing Fat as a Busy Parent
- Sleep. 2015 Jun 1; 38(6): 843–844. Recommended Amount of Sleep for a Healthy Adult: A Joint Consensus Statement of the American Academy of Sleep Medicine and Sleep Research Society.
- Circulation. 2016 Nov 1; 134(18): e367–e386. Sleep Duration and Quality: Impact on Lifestyle Behaviors and Cardiometabolic Health.
- CDC Weekly, February 19, 2016, 65(6);137–141. Prevalence of Healthy Sleep Duration among Adults — United States, 2014.
- Sleep Breath. 2019 Dec;23(4):1035-1045. Dose-response association between sleep duration and obesity risk: a systematic review and meta-analysis of prospective cohort studies.
- J Hum Nutr Diet. 2021 Apr;34(2):273-285. The influence of sleep health on dietary intake: a systematic review and meta-analysis of intervention studies.
- Sleep Medicine Reviews Volume 45, June 2019, Pages 18-30. Effects of sleep restriction on metabolism-related parameters in healthy adults: A comprehensive review and meta-analysis of randomized controlled trials.
- JAMA Intern Med. February 7, 2022. Effect of Sleep Extension on Objectively Assessed Energy Intake Among Adults With Overweight in Real-life Settings.