Why Sleep Is Important for Recovery, Fat Loss and Muscle

Sleep is when your body repairs muscle, your brain clears waste and stores what you learned, and your hunger hormones reset. Adults need at least seven hours a night. Sleeping less raises hunger, makes dieting harder and causes you to lose more muscle and less fat on the same calories. For recovery, sleep matters more than any supplement.

How much sleep do adults need?

At least seven hours a night on a regular basis, according to a joint statement from the American Academy of Sleep Medicine and the Sleep Research Society (Watson et al., 2015). Many people who train hard do better with eight or more.

What happens to your brain during sleep?

Two big things. First, during sleep the brain clears out waste products faster. In animal research, the space between brain cells expanded during sleep and waste was cleared much more quickly than when awake (Xie et al., 2013). Second, sleep is when you lock in what you learned that day, including new skills like a squat pattern or a lifting cue.

Poor sleep also makes emotions harder to handle. Small stresses feel bigger, and that is when people skip workouts and reach for comfort food.

How does poor sleep affect fat loss?

It makes it much harder. In healthy young men, two nights of four hours of sleep raised ghrelin, the hunger hormone, by 28 percent and lowered leptin, the fullness hormone (Spiegel et al., 2004). In a dieting study, people who slept 5.5 hours lost about half as much fat and more muscle than when they slept 8.5 hours on the same diet (Nedeltcheva et al., 2010).

Short sleep is also tied to poorer blood sugar control and higher risk of heart disease and other conditions over time (NHLBI).

How does sleep affect muscle and strength?

Muscle repair, hormone release and nervous system recovery all lean on sleep. Short sleep can also lower testosterone in men. One week of five hour nights cut daytime testosterone 10 to 15 percent in young men (Leproult and Van Cauter, 2011). Most of my clients notice that after a bad night their lifts feel heavy, their focus is off and their joints ache more.

Is caffeine hurting my sleep?

Possibly. Caffeine taken six hours before bed still cut total sleep by about an hour in one study (Drake et al., 2013). Caffeine can mask tiredness during the day, but you pay it back at night. Cut it off by early afternoon.

How can I sleep better?

This is the checklist I give clients:

1. Keep the same bed and wake time every day, weekends included, within about an hour.
2. Get daylight in your eyes within an hour of waking.
3. Cut caffeine after about 1 or 2 pm.
4. Avoid alcohol close to bed. It knocks you out but wrecks sleep quality. Read if you need alcohol to sleep, read this.
5. Keep your room dark, quiet and cool.
6. Put your phone away 30 to 60 minutes before bed.
7. Finish big meals two to three hours before bed.
8. Do hard training earlier in the day if late sessions keep you wired.
9. Wind down with a short routine: shower, reading, light stretching or slow breathing.

When should I see a doctor about sleep?

If you snore loudly, stop breathing or gasp during sleep, wake up tired after a full night, or have insomnia most nights for weeks, talk to a doctor. Sleep apnea is common and treatable, and it affects weight, blood pressure and energy.

For more on recovery, read over-training or poor recovery and supplements for energy, focus and sleep. If you want a plan that builds in recovery, take the XPL quiz.