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Sleep Stages Critical to Optimal Muscle Growth and Fat Loss


calendar-iconFebruary 4, 2019

Foundational Sleep Series


Sleep can aid both fat loss and muscle growth.

Believe it or not, there are actually many stages to how you sleep each night. It is helpful to understand the structure of sleep so you can understand its potential to positively impact your goals.

While there is still a great deal of mystery around why exactly we need to sleep, research has revealed that there are distinct and identifiable stages of sleep. Moreover, each stage of sleep can be linked to a specific form of recovery and utility, all of which can aid in your journey to optimal fitness.

So what are these sleep stages, and how can they help you lose fat and gain muscle? We're breaking it all down here in this post.

Sleep Stage 1: N1

When you first fall asleep, you enter NREM (Non-Rapid Eye Movement) sleep. NREM is comprised of three stages the first stage being N1.1,2

N1 is the transitional stage between being awake and falling asleep, also known as light sleep, and is marked by both mental and physical relaxation.3 This stage is sometimes accompanied by a feeling of falling, causing you to suddenly wake up.4

In essence, N1 is the gateway to the deeper stages of sleep.

Sleep Stage 2: N2

N2 is the onset of sleep, during which you become disengaged from your surroundings.3

When you reach this stage of sleep, your body temperature drops, your heart rate slows, your breathing becomes more regular, and your muscles relax completely. N2 is your first step into complete rest, and the entryway into N3, which is crucial to physical recovery.

Sleep Stage 3: N3

Lack of sleep appears to result in lower leptin and higher ghrelin levels, both of which make you eat more and gain weight.

National Sleep Foundation

N3 is the stage of deep, restorative sleep.3 During this stage, your blood pressure drops, your breathing slows, blood flow to muscles increases.3

During this stage of NREM, your tissue and muscle repairs themselves. For this reason, N3 is paramount to muscle growth.3 Hormones such as growth hormone are released and regulated during this stage, as well as hormones that contribute to muscle growth, muscle retention, fat loss, fat storage, and recovery.3 Lastly, N3 boosts immune function in your body, keeping your guard up against colds, flu's, and other attacks on your immune system.3

Has your muscle growth stalled despite a proper fitness and nutrition regimen? The "common cold" becoming a little too common? You might be in sore need of some N3 sleep.

After N3, you'll briefly re-enter sleep stages N2 and N1 before entering into the ultimate sleep stage: REM sleep.4

Sleep stage 4: REM Sleep

REM sleep is thought to play a role in memory consolidation, the synthesis and organization of cognition, and mood regulation.

National Sleep Foundation

REM (Rapid Eye Movement) sleep provides energy to the brain and body, supports daytime performance and alertness, consolidates long term memory, and solidifies new muscle memory.3,4

You'll enter REM sleep about 90 minutes after falling asleep.3 During this time, your muscles completely relax and your eyes dart back and forth (hence the name).4 Without proper REM sleep, you'll find yourself sluggish throughout the day, slow to the take, and you won't fully solidify any new skills or information you take in throughout the day, physically or mentally.

Does the idea of going to the gym sound like nails on a chalkboard? Is the couch constantly calling your name? Lack of REM sleep may be the culprit.

Following REM Sleep, you'll reenter N1 and repeat the cycle in full 4-5 times on a good nights rest (Fig 1).4

The Takeaway

Knowing the utility of each sleep stage should show you why getting a full nights rest is so important.

By depriving yourself of sleep, you are depriving yourself of the one or more sleep cycles (figure above). The sleep cycles are pivotal for muscle growth, fat loss, as well as a myriad of hormones and bodily functions that indirectly support muscle growth and fat loss.

With a basic understanding of the structure of sleep, we can now address the components of a full night’s rest: quantity, consistency, and continuity.


  1. Aserinsky E, Kleitman N. Regularly occurring periods of eye motility, and concomitant phenomena, during sleep.
    Science. 1953;118:273-274 Link
  2. Rechtschaffen A. Current perspectives on the function of sleep. Perspectives in Biology and Medicine.
    1998;41:359-390. Link
  3. National Sleep Foundation, The Sleep-Wake Cycle: Its Physiology and Impact on Health, Arlington: NSF, 2006. Available at: Link
  4. Maas, James B., et al. Sleep for Success: Everything You Must Know About Sleep but Are Too Tired to Ask. Author House, 2011. Link
Date Created: February 4, 2019

Last Updated: April 2, 2020

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