Lose Fat & Build Muscle by Sleeping


Even if you eat well and exercise regularly, if you’re not getting enough sleep you might be making it harder for yourself to lose fat and/or build muscle.


Most people know that good nutrition and exercise are some of the foundations of a healthy lifestyle but many people these days forget about (or downright ignore) the importance of another foundation of health: Sleep.


Are you getting enough sleep?

Recent studies have shown that in the last 50 years, the amount of sleep in some developed countries has dropped by as much as 2 hours {1} so it’s pretty likely that this applies to most people. In this article I want to make it very clear just how important getting enough, quality sleep actually is.


If your goal is:

  • Losing body fat
  • Building lean muscle
  • Improved sports performance
  • General health

...then you really need to prioritize your sleep (along with your nutrition and training).


Lack of Sleep and Weight Gain

The evidence is pretty damn conclusive; people who sleep less are much more likely to be obese {2,3}. On average, shorter sleepers have more than 50% higher risk of becoming  obese than people who get adequate sleep (which the studies estimate to be from 7-9 hours) {2}.


One study {4} really hit the nail on the head here: “It is paradoxical that sleeping, the most sedentary of all activities, may be associated with leanness”. Why is it that spending less time in the sack causes you to gain weight?


Well the reason seems to boil down to one major factor: Appetite. Multiple studies have shown that a lack of sleep or sleep disturbances lead to changes in the body’s levels of two hormones, ghrelin and leptin. Specifically, sleep-loss causes leptin levels to drop and ghrelin levels to go up which causes people to feel more hunger {3-5}. In fact, another meta-analysis showed that lack of sleep can cause people to eat almost 400 calories extra per day {6}. With an extra 400 calories a day, anyone would quickly put on weight.


The get even more deep into the research, when healthy and lean people lack sleep or have disturbed sleep certain parts of their brains connected with “hedonic” eating become more active {7}. These areas of the brain are usually more active in obese people and cause them to anticipate greater rewards when they see images of food. When people expect a greater reward from food they tend to overeat; they expect to enjoy it more! On top of that, sleep loss seems to have even greater effects on people who would already be classed as “emotional eaters”. A lack of sleep can act as a stressor in these people, which may push them to eat (by the mechanisms I just mentioned) to try and relieve the added stress.


So if you already find yourself running for the Häagen-Dazs whenever you get upset, it might be particularly important for you to get enough sleep to keep it (somewhat) under control.


My own food cravings

I struggled with emotional eating and trying to control my weight for years. I would often go through extended periods of eating well and feeling great, interspersed with times when I, for some reason, would lose control over what I ate.


Eventually I noticed a pattern myself, whereby a day of uncontrolled eating was frequently preceded by a night of very little or just bad sleep. The lack of sleep actually caused me to have more food cravings and feel hungrier the next day. Once I figured out the connection, I started making sleep even more of a priority and if I did miss out on sleep I learned to take extra care to avoid situations where I might be tempted to overeat (like visiting the ice-cream section in the supermarket).


My own experience, backed up by the huge amount of scientific evidence available is enough for me to consider “getting enough sleep” to be absolutely essential for achieving and maintaining a healthy weight.


How Sleep builds your Muscles

So, one of the ways that losing sleep can hinder your weight loss goals is by causing you to eat more, but are they’re any other ways that missing out on your forty winks can slow down your attempts at fitting into skinny jeans?


When people try to lose weight, it’s almost universally understood that what they actually want to do is lose body fat. People generally don’t want to lose muscle mass; it keeps you strong and healthy and aesthetically, muscle generally looks good, especially when you lose some of the fat covering it. So in my opinion...


...the real goal of weight loss is to lose as much body fat while maintaining as much muscle mass as possible.


Well, it turns out that sleep plays a big role here too. A lack of sleep can actually cause you to lose more muscle than fat when losing weight. In one study {5}, 2 groups of people were fed the same, low-calorie diet to make them lose weight. The only difference was that one group got to spend 8.5 hours in bed while the other group only got to spend 5.5 hours in bed. Both groups lost about the same amount of weight with the 8.5 hour group losing about 50% of the weight as muscle (normal for weight loss without weight training to maintain muscle mass). However the group that slept less lost almost 80% of that weight as muscle mass. That’s right, instead of losing fat they were losing mostly muscle.


On top of that, they had higher levels of ghrelin, which probably made them feel hungrier than the group that was sleeping enough. Ghrelin also plays a role in sparing fat, which is why the sleep-restricted group lost more muscle instead.


Lift, Eat, Sleep, Repeat!

Most people who lift weights know that in order to get the most out of your training, you need to eat well and rest plenty to get your muscles to grow. If you don’t get enough sleep, then that’s not enough rest and you won't be able to maximize your potential muscle gains and there’s some scientific evidence to show us why {8}.


When you are chronically sleep deprived, your body starts to produce less of two hormones that are needed for muscle growth: Testosterone and IGF-1. These hormones usually have anabolic (muscle building effects) in the body so if their levels are lower (because of lack of sleep or other reasons) then your body just can’t build new muscle (through protein synthesis) as well as it should.


On top of that, like we mentioned earlier, lack of sleep is like a stressor so it causes an increase in stress hormones like cortisol. These are catabolic hormones meaning, they cause breakdown of tissues (in this case, muscle) and prevent protein synthesis meaning less muscle is built than could be it someone is sleeping well.


It seems pretty clear that if building muscle and increasing strength is goal of yours (which I feel it should be for many people) then prioritizing sleep is essential to increase muscle protein synthesis and reduce muscle breakdown.


The Diabetes Connection

If increased appetite, weight gain and muscle loss aren’t enough to convince you that sleep loss is bad news then here’s something else to take very seriously: diabetes. Type 2 Diabetes (a loss of control of blood sugar that can be fatal if left untreated) is caused when your body becomes less sensitive to insulin (a hormone that controls the levels of glucose in the body). This type of diabetes often goes hand in hand with obesity and can lead to metabolic syndrome (a group of different conditions including obesity, diabetes, high cholesterol, high blood pressure etc. that is becoming increasingly common in the modern world) {9}.


Interestingly sleep loss can actually reduce insulin-sensitivity in people who are otherwise healthy and lean, meaning their body can’t handle glucose as well as normal {10,11}, which is well known to be a stage in the development of full-blown diabetes. The combination of weight gain, lower insulin sensitivity and other health effects caused by not sleeping enough seriously increases your risk of developing metabolic syndrome.


Even more important for kids

The interesting thing about the studies on the relationship between lack of sleep and weight gain is that the relationship seems to be even stronger in kids {2,3}. In fact, one meta-analysis found that for every hour of sleep that a child lost their risk of obesity increased 5 fold {2}.


Children in general need to sleep more than adults (the need for sleep seems to decrease the older we get) {3} so ensuring that your children get enough, high quality sleep should be a priority amongst parents (I’m sure most parents are thinking “easier said than done”). Honestly, setting up good sleeping habits at a young age could benefit your children’s health well into adulthood. Enforcing stricter bedtimes and limiting the access kids have to TV/Phones/Computers etc. at nighttime might be worth the added effort in the long run.


The younger the child, the more sleep they need to help them grow and develop in a healthy way
The younger the child, the more sleep they need to help them grow and develop in a healthy way

More is not necessarily better!!

We’re constantly told that 7-9 hours is the “ideal” amount of time that adults should sleep and the two meta-analysis (a combination of multiple studies that uses the greater amount of data to give a better picture of the current evidence) mentioned above {2,3} both suggest that the relationship between obesity and sleep time follows a U-shaped curve. That means that if 7-9 hours is the ideal (the bottom of the “U”) sleeping less OR more than that increases your risk of obesity. So just because 8 hours is good doesn’t mean that 10 hours in bed is better!


I would say that the ideal sleep time differs from person to person but exercise definitely increases the amount you need to sleep so bear that in mind if you exercise regularly (which you should). I find myself that on vacation, if I'm not exercising, then 6-7 hours of sleep is fine but when I'm training hard, if I don't get a solid 8 hours of sleep I'll really feel it the next day.


Make Sleep a Priority

We live in world filled with distractions that cause us to sleep less and less. Unfortunately that can have major negative effects on your waistline, your muscles and your health in general. One night of bad sleep every now and then isn’t going to be a problem but when it becomes chronic, when you sleeping very little becomes the norm (which happens with many people in todays world) then those problems are going to rear their ugly heads.


It may be easier said than done but prioritizing your sleep needs to become as important as eating a healthy diet and exercising regularly. They all work together to help you become the healthiest possible version of yourself.


Sleep well, folks.


  1. National Sleep Foundation. Sleep in America Poll. Washington DC; 2005
  2. Cappuccio FP, Taggart FM, Kandala N-B, Currie A, Peile E, Stranges S, et al. Meta-analysis of short sleep duration and obesity in children and adults. Sleep. 2008;31(5):619–26.
  3. Patel SR, Hu FB. Short sleep duration and weight gain: a systematic review. Obesity. 2008;16(3):643–53.
  4. Chaput JP, Després JP, Bouchard C, Tremblay A. Short sleep duration is associated with reduced leptin levels and increased adiposity: results from the Quebec family study. Obesity. 2007;15(1), 253-261.
  5. Nedeltcheva A V., Kilkus JM, Imperial J, Schoeller DA, Penev PD. Insufficient sleep undermines dietary efforts to reduce adiposity. Ann Intern Med. 2010;153(7):435–41.
  6. Al Khatib HK, Harding SV, Darzi J, Pot GK. The effects of partial sleep deprivation on energy balance: a systematic review and meta-analysis. Eur J Clin Nutr. 2016.
  7. Benedict C, Brooks SJ, O’Daly OG, Almèn MS, Morell A, Åberg K, et al. Acute sleep deprivation enhances the brain’s response to hedonic food stimuli: An fMRI study. J Clin Endocrinol Metab. 2012;97(3).
  8. Dweck JS, Jenkins SM, Nolan LJ. The role of emotional eating and stress in the influence of short sleep on food consumption. Appetite. 2014;72:106–13.
  9. Alberti KGMM, Zimmet P, Shaw J. Metabolic syndrome--a new world-wide definition. A Consensus Statement from the International Diabetes Federation. Diabet Med. 2006;23(5):469–80.
  10. Broussard JL, Ehrmann DA, Van Cauter E, Tasali E, Brady MJ. Impaired Insulin Signaling in Human Adipocytes After Experimental Sleep Restriction. Ann Intern Med. 2012;157(8):549–57.
  11. Broussard J, Brady MJ. The impact of sleep disturbances on adipocyte function and lipid metabolism. Best Prac Res Clin Endo Met. 2010;24(5), 763-773.

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