How sleep affects your recovery, muscle and fat loss

Sleep isn't time off from training. It's when most of your recovery actually happens. While you sleep, your body repairs muscle, regulates stress hormones and consolidates the movement skills you worked on in your workouts. This guide covers what the research says about sleep and performance, what happens when you don't get enough, and how sleep affects muscle growth and fat loss. You'll also find practical habits, the studies behind them and a few products that can help.

What sleep does for performance

Study after study finds that athletes who get 7 to 9 hours of sleep react faster, last longer and get hurt less. A few examples:

• Mah et al. (2011) had college basketball players sleep longer, and their sprint times and shooting accuracy improved significantly.
  (Mah et al., 2011)

• Fullagar et al. (2015) reviewed how even moderate sleep loss hurts both the physical and mental side of exercise.
  (Fullagar et al., 2015)

• Watson (2017) reviewed the research and found that longer, better sleep is linked to better performance and fewer injuries and illnesses in athletes, and that most athletes don't get enough of it.
  (Watson, 2017)

The graph below shows how performance changes with sleep duration:

Is more than 9 hours better?

Seven to nine hours is the usual target for most adults and athletes. So what happens if you sleep longer than that? Here's what the research shows:

• It can help during hard training blocks. Some athletes, especially during heavy training or while coming back from an injury, may do better with the occasional longer night. Mah et al. (2011) saw performance improve when players aimed for 10 hours in bed each night.

• The returns level off. For most people, the gains above 9 hours flatten out. Extra sleep doesn't keep adding equal amounts of recovery or performance.

• Very long sleep every night has been linked to health problems. In the general population, regularly sleeping very long hours is associated with more inflammation and a higher risk of dying early. Those links may come from underlying health conditions, not from the extra sleep itself.
  (Irwin et al., 2016; Cappuccio et al., 2010)

So extra sleep can help when you're training hard or recovering, but most athletes will perform best somewhere in the 7 to 9 hour range. Pay attention to how you feel and how your training goes, and adjust from there.

What short sleep costs you

Seven to nine hours supports recovery. Falling well short of that has real consequences, and the research is fairly clear on what they are.

Sleeping 2 to 4 hours a night

• Your thinking falls apart. Extreme sleep loss badly hurts concentration, decision making and memory.
  (Durmer & Dinges, 2005)

• You get hurt more. In one study of teenage athletes, those who slept less than 8 hours a night were 1.7 times more likely to have been injured than those who slept 8 or more.
  (Milewski et al., 2014)

• Your hormones go off. Too little deep sleep cuts growth hormone production, which your muscles need to repair, and disrupts other hormones too.
  (Van Cauter & Plat, 1996)

• Your mood suffers. Ongoing poor sleep is linked to more stress and low mood. People with insomnia are about twice as likely to go on to develop depression.
  (Baglioni et al., 2011)

Sleeping 4 to 6 hours a night

• Recovery is incomplete. Four to six hours beats two to four, but it still isn't enough for your muscles to fully recover and repair. In one study, five nights of 4 hours in bed lowered the rate at which muscle rebuilds its protein.
  (Saner et al., 2020)

• You react more slowly. In a lab study, two weeks of 6 hours a night steadily wore down attention and reaction time, and people didn't feel nearly as impaired as they were.
  (Van Dongen et al., 2003)

• Inflammation goes up. Short and disturbed sleep have both been linked to higher levels of inflammation markers like C-reactive protein, which may slow recovery.
  (Irwin et al., 2016)

How to sleep better

Good sleep habits (what researchers call sleep hygiene) can make a big difference to how well you sleep. These are the ones with evidence behind them:

• Keep the same schedule.
  Going to bed and getting up at the same time every day keeps your body clock steady. In a study of college students, those with irregular sleep schedules had later body clocks and worse grades than students who kept a regular schedule.
  (Phillips et al., 2017)

• Cut back on screens before bed.
  Putting screens away at least an hour before bed helps protect your melatonin production. In one study, reading on a backlit eReader before bed instead of a printed book delayed melatonin, made it take longer to fall asleep and left people less alert the next morning.
  (Chang et al., 2015)

• Have a wind down routine.
  Reading, meditation or some gentle stretching tells your body it's time to settle. A meta analysis of trials in people with insomnia found mindfulness meditation gave modest improvements in sleep quality and time spent awake at night.
  (Gong et al., 2016)

• Fix your bedroom.
  Dark, cool and quiet is what you're after. A hot bedroom means more time awake and less deep and REM sleep, and nighttime noise disturbs sleep too.
  (Okamoto-Mizuno & Mizuno, 2012; Basner et al., 2014)

Sleep, hormones, muscle and fat loss

A lot of what drives muscle growth and fat loss happens hormonally, and much of it happens while you sleep. In deep sleep your body releases anabolic hormones, including growth hormone and testosterone. They matter for two things:

• Building muscle.
  Growth hormone and testosterone drive muscle protein synthesis and repair. Sleep less and you release less of them, which slows muscle growth and recovery. One week of 5 hours a night lowered testosterone in young men, and a single night without sleep cut muscle protein synthesis by 18%.
  (Van Cauter & Plat, 1996; Leproult & Van Cauter, 2011; Lamon et al., 2021)

• Losing fat.
  Enough sleep helps keep cortisol in check. When sleep loss pushes cortisol up, it breaks down muscle and encourages fat storage. Poor sleep also affects insulin sensitivity and shifts your appetite hormones (less leptin, more ghrelin), so you end up hungrier. In one diet study, people who got 5.5 hours in bed a night instead of 8.5 lost the same weight, but much less of it was fat.
  (Spiegel et al., 2004; Knutson et al., 2007; Nedeltcheva et al., 2010; Lamon et al., 2021)

In other words, if you're training to change your body composition, sleep is part of the program. The hormones released during deep sleep help you build muscle and lose fat, so short nights take something away from every session.

How sleep affects muscle growth and fat loss

The chart below is an estimate of how more sleep might improve muscle growth and fat loss. (The values are hypothetical. They're there to show the trend based on current research, not to give exact numbers.)

Products and supplements that can help

Sleep gear

• Sleep trackers.
  A device like the Oura Ring, WHOOP strap or a Fitbit shows you how well you're actually sleeping.

• Blue light blocking glasses.
  Screen light at night can delay your body clock, so these may be worth trying if your evenings involve a lot of screen time. The research on the glasses themselves is mixed, though, so putting the screen away is the surer bet.
  (Chang et al., 2015)

• Good bedding.
  A supportive mattress and blackout curtains go a long way toward a better sleep environment. In one study, people who swapped beds they'd had for years for new medium firm ones reported better sleep and less back pain.
  (Jacobson et al., 2009)

• A white noise machine.
  Some people find it helps them stay asleep, especially in a noisy home. A systematic review rated the evidence that it improves sleep as very low quality, so treat it as a personal preference, not a fix.
  (Riedy et al., 2021)

Supplements to consider

• Magnesium bisglycinate.
  In a trial in older adults with insomnia, 500 mg of magnesium a day for 8 weeks helped them fall asleep faster and sleep longer than a placebo. Bisglycinate is a well tolerated form. Look for a product that's been third party tested.
  (Abbasi et al., 2012)

• ZMA.
  ZMA combines zinc, magnesium and vitamin B6, and it's often sold for sleep, recovery and muscle growth. The evidence is thin. In a study of trained men, 8 weeks of ZMA didn't change their strength or their testosterone levels compared with a placebo. If you want to try it, stick to the dose on the label rather than building your own high dose stack.
  (Wilborn et al., 2004)

Talk to your doctor or another healthcare professional before you start any new supplement.

If you change one thing

Make it your schedule. Going to bed and getting up at the same time every day is free, the research supports it, and it makes the other habits on this list easier to keep. Gear and supplements sit on top of that. They don't replace it.

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References

1. Mah CD, Mah KE, Kezirian EJ, et al. (2011). The effects of sleep extension on the athletic performance of collegiate basketball players. Sleep, 34(7):943-50. PubMed

2. Fullagar HH, Skorski S, Duffield R, et al. (2015). Sleep and athletic performance: the effects of sleep loss on exercise performance, and physiological and cognitive responses to exercise. Sports Medicine, 45(2):161-86. PubMed

3. Watson AM (2017). Sleep and Athletic Performance. Current Sports Medicine Reports, 16(6):413-418. PubMed

4. Irwin MR, Olmstead R, Carroll JE (2016). Sleep Disturbance, Sleep Duration, and Inflammation: A Systematic Review and Meta-Analysis of Cohort Studies and Experimental Sleep Deprivation. Biological Psychiatry, 80(1):40-52. PubMed

5. Cappuccio FP, D'Elia L, Strazzullo P, et al. (2010). Sleep duration and all-cause mortality: a systematic review and meta-analysis of prospective studies. Sleep, 33(5):585-92. PubMed

6. Durmer JS, Dinges DF (2005). Neurocognitive consequences of sleep deprivation. Seminars in Neurology, 25(1):117-29. PubMed

7. Milewski MD, Skaggs DL, Bishop GA, et al. (2014). Chronic lack of sleep is associated with increased sports injuries in adolescent athletes. Journal of Pediatric Orthopedics, 34(2):129-33. PubMed

8. Van Cauter E, Plat L (1996). Physiology of growth hormone secretion during sleep. The Journal of Pediatrics, 128(5 Pt 2):S32-7. PubMed

9. Baglioni C, Battagliese G, Feige B, et al. (2011). Insomnia as a predictor of depression: a meta-analytic evaluation of longitudinal epidemiological studies. Journal of Affective Disorders, 135(1-3):10-9. PubMed

10. Saner NJ, Lee MJ, Pitchford NW, et al. (2020). The effect of sleep restriction, with or without high-intensity interval exercise, on myofibrillar protein synthesis in healthy young men. The Journal of Physiology, 598(8):1523-1536. PubMed

11. Van Dongen HP, Maislin G, Mullington JM, et al. (2003). The cumulative cost of additional wakefulness: dose-response effects on neurobehavioral functions and sleep physiology from chronic sleep restriction and total sleep deprivation. Sleep, 26(2):117-26. PubMed

12. Phillips AJK, Clerx WM, O'Brien CS, et al. (2017). Irregular sleep/wake patterns are associated with poorer academic performance and delayed circadian and sleep/wake timing. Scientific Reports, 7(1):3216. PubMed

13. Chang AM, Aeschbach D, Duffy JF, et al. (2015). Evening use of light-emitting eReaders negatively affects sleep, circadian timing, and next-morning alertness. Proceedings of the National Academy of Sciences of the United States of America, 112(4):1232-7. PubMed

14. Gong H, Ni CX, Liu YZ, et al. (2016). Mindfulness meditation for insomnia: A meta-analysis of randomized controlled trials. Journal of Psychosomatic Research, 89:1-6. PubMed

15. Okamoto-Mizuno K, Mizuno K (2012). Effects of thermal environment on sleep and circadian rhythm. Journal of Physiological Anthropology, 31(1):14. PubMed

16. Basner M, Babisch W, Davis A, et al. (2014). Auditory and non-auditory effects of noise on health. The Lancet, 383(9925):1325-1332. PubMed

17. Leproult R, Van Cauter E (2011). Effect of 1 week of sleep restriction on testosterone levels in young healthy men. JAMA, 305(21):2173-4. PubMed

18. Lamon S, Morabito A, Arentson-Lantz E, et al. (2021). The effect of acute sleep deprivation on skeletal muscle protein synthesis and the hormonal environment. Physiological Reports, 9(1):e14660. PubMed

19. Spiegel K, Tasali E, Penev P, et al. (2004). Brief communication: Sleep curtailment in healthy young men is associated with decreased leptin levels, elevated ghrelin levels, and increased hunger and appetite. Annals of Internal Medicine, 141(11):846-50. PubMed

20. Knutson KL, Spiegel K, Penev P, et al. (2007). The metabolic consequences of sleep deprivation. Sleep Medicine Reviews, 11(3):163-78. PubMed

21. Nedeltcheva AV, Kilkus JM, Imperial J, et al. (2010). Insufficient sleep undermines dietary efforts to reduce adiposity. Annals of Internal Medicine, 153(7):435-41. PubMed

22. Jacobson BH, Boolani A, Smith DB (2009). Changes in back pain, sleep quality, and perceived stress after introduction of new bedding systems. Journal of Chiropractic Medicine, 8(1):1-8. PubMed

23. Riedy SM, Smith MG, Rocha S, et al. (2021). Noise as a sleep aid: A systematic review. Sleep Medicine Reviews, 55:101385. PubMed

24. Abbasi B, Kimiagar M, Sadeghniiat K, et al. (2012). The effect of magnesium supplementation on primary insomnia in elderly: A double-blind placebo-controlled clinical trial. Journal of Research in Medical Sciences, 17(12):1161-9. PubMed

25. Wilborn CD, Kerksick CM, Campbell BI, et al. (2004). Effects of Zinc Magnesium Aspartate (ZMA) Supplementation on Training Adaptations and Markers of Anabolism and Catabolism. Journal of the International Society of Sports Nutrition, 1(2):12-20. PubMed

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