Sleep: The Ultimate Recovery Tool

When it comes to wellness, sleep is a non-negotiable cornerstone: too little not only harms our immediate quality of life, but also contributes to longer-term disease risk, weakened immunity, and even earlier mortality.^[1]

Despite its importance, sleep tends to be viewed more as a luxury than a necessity. It’s often the first thing we sacrifice in order to meet the demands of a busy day, and sleep quality is rarely given as much attention as other major lifestyle components like diet and exercise.

Sleep can feel like a passive health tool compared to the seemingly more “active” behaviors of eating or physically moving. But the truth is, just like the adage “you can't out-exercise a bad diet,” you also can't out-eat or out-exercise poor sleep.

Putting effort into optimizing our sleep routine can have a profound effect on our health. In fact, getting high-quality sleep—and enough of it nightly—brings wide-ranging benefits for mental function, physical performance, injury recovery, body composition, hormonal health, and more!

What happens when we sleep?

While it might seem like most of our bodies’ systems shut down during sleep, sleep is far from a passive activity: it’s actually a critical time for repair and rebuilding.

Every night, we cycle repeatedly through 4 different stages of sleep, all of which serve specific functions in helping us wake up feeling refreshed and restored. Those sleep stages are:

• Awake time, which includes the time we spend in bed before and after we actually fall asleep, as well as brief awakenings throughout the night.
• Light sleep, in which our muscles relax, heart rate decreases, body temperature drops, and breathing slows. We spend about 50% of our sleep time here!
• Deep sleep, in which blood flow increases to muscles, blood pressure drops, brain waves become longer and slower, and waking up becomes difficult. Most of our deep sleep occurs during the earlier part of the night.
• Rapid eye movement (or REM) sleep, in which our eyes move rapidly behind our eyelids, breathing and heart rate increase, brain activity rises, and vivid dreams can occur.

Deep sleep and REM are the most critical times for repair work. Specifically, during these stages, the body (especially the brain) carries out important functions such as:

• Storing new information to promote memory and learning^[2]
• Erasing synapses so that we can “forget” unneeded information and keep our brain networks uncluttered^[3]
• Repairing and building tissue^[4]
• Regenerating cells (including in the skin, intestine, bones, and cartilage)^[4]
• Processing and consolidating emotional memory^[5]
• Clearing out metabolic waste products that our brains generate while we’re awake^[3]
• Releasing growth hormone (for men, sleep triggers the biggest growth hormone surge of the day, as cortisol drops and melatonin secretion spikes)^[6] [7]

In other words, sleep is a surprisingly action-packed time, as far as our bodies are concerned!

The consequences of poor sleep

We all know that feeling of waking up groggy, wishing we could hit the “snooze” button a few more times before dragging ourselves out of bed.

But the effects of inadequate or poor-quality sleep go much further than a rough morning and tired day. Lack of sleep results in a slew of hormonal, metabolic, and immune changes that negatively impact many areas of our lives.

Scientists are still studying all the ways that poor sleep affects human health, but so far, we know that even short-term sleep deprivation can cause the following problems:

• Recovery takes longer. Lack of sleep results in hormonal changes that break down muscle—including an increase in cortisol and decreases in testosterone and Insulin-like Growth Factor 1 (IGF-1).^[8] This impairs our ability to recover from exercise or injury, as our muscles are stuck in “breakdown” mode instead of properly healing and repairing. In one study, a single night of sleep deprivation led to a 18% reduction in muscle protein synthesis, as well as a 21% increase in cortisol levels, and a 24% decrease in testosterone.^[9]
• Appetite regulation suffers. Sleep deprivation causes changes in appetite-related hormones such as ghrelin, leptin, and insulin, leading to increased hunger and energy intake throughout the day—particularly from foods high in fat and carbohydrates.^[10] These appetite changes occur from as little as one night of poor sleep.^[11]
• Mood is negatively impacted. A night of poor sleep has immediate repercussions for our mood—including heightening feelings of anxiety, depression, anger, and aggression the next day.^[12] [13] This is specifically linked to lack of REM sleep, which is needed for amygdala adaptation (the emotional processing center of the brain).^[14] [15]
• Cognitive performance and memory declines. When we don’t get enough sleep, our ability to think clearly and process information takes a significant hit. Studies show that a week of reduced sleep causes a deterioration in working memory, executive function, and sustained attention—and what’s more, these functions remain impaired even after two nights of full sleep.^[16]
• Immune function weakens. Sleep is imperative for maintaining immune system homeostasis, and getting too little of it lowers our defenses against pathogens—leading to an increased risk of infection from bacteria, viruses, and even parasites.^[17] In fact, our desire to sleep more when we’re sick is due in large part to the immune regulation that happens when we’re sleeping.^[18]

Meanwhile, chronic sleep deprivation (less than 5 hours per night) brings additional damage over time, including an increased risk of many health conditions:

• Type 2 diabetes (due to the impact of sleep on blood sugar control and insulin regulation)^[19]
• Heart disease and heart attacks^[20]
• Stroke^[21]
• High blood pressure^[22]
• Obesity (due to changes in hormones that regulate hunger and metabolism, as well as increased daily energy intake)^[10]
• Chronic depression^[23]
• Cancer^[24] [25]
• Kidney disease^[26]
• Alzheimer’s disease and dementia^[27]
• Autoimmune disease (including lupus, rheumatoid arthritis, ankylosing spondylitis, and Sjögren's syndrome)^[28]
• Fibromyalgia^[29]
• Periodontal disease^[30]
• Osteoporosis (due to sleep facilitating important bone-remodeling processes)^[31]

Unmanaged sleep disturbances, such as sleep apnea, can also contribute to these health risks by interrupting our sleep cycles and reducing the amount of time we spend in deep sleep.^[32] So, even if we’re physically in bed for a reasonable amount of time, the quality of the sleep we’re getting matters too!

How much sleep do we need?

The optimal amount of sleep varies from person to person, influenced by factors like age, health status, genetics, and more. However, the current consensus is that most adults require about 7 to 8 hours of sleep per night to function their best.^[33] Regularly sleeping less than 7 hours per night begins increasing the risk of adverse health outcomes, accidents, and performance impairment.^[33]

Some circumstances can temporarily increase our sleep needs—such as being sick, recovering from sleep debt, or performing strenuous activity during the day.^[33] In these situations, it’s normal to need more than 8 hours of sleep in order to feel fully rejuvenated.

As a general rule, if you wake up feeling well-rested and stay alert throughout the day, you’re probably getting the right amount of sleep.^[34]

How do we improve our sleep?

Taking measures to improve the quality and quantity of our sleep is one of the most valuable things we can do for our health. But how do we go about doing so?

The answer lies in optimizing our sleep hygiene—a term referring to the behaviors and environment we create to support optimal sleep.

Good sleep hygiene means making choices that support our circadian rhythms (the body’s daily sleep-wake cycles) and our sleep drive (a biological urge similar to hunger, where the desire for sleep builds throughout the day).

During the daytime, there are a number of things we can do to improve our sleep hygiene. These include:

• Getting outdoor sun exposure. Getting outdoors and into the sunlight helps regulate the body’s circadian rhythms, especially melatonin secretion—in turn making it easier to fall asleep at night.^[35]
• Enjoying daily physical activity. Regularly moving our bodies increases sleep quality and feelings of being fully rested.^[36]
• Sticking to routine wake-up and sleep times. Structured sleep schedules help stabilize circadian rhythms and promote healthy sleep patterns.^[37]
• Limiting alcohol intake, especially within a few hours of bed. While alcohol might seem to help with sleep due to inducing feelings of drowsiness, research shows it actually reduces the total amount of REM sleep we get, and significantly disrupts sleep quality in the second half of the night.^[38]
• Avoiding caffeine after mid-afternoon. Caffeine consumption has been linked to a reduction in both sleep time and sleep quality, even if consumed as much as 6 hours before bed.^[39]

Meanwhile, our nighttime habits and environment also have a huge influence on our sleep. Consider trying these tips:

• Commit to a bedtime. While it might be tempting to fully follow your instincts where sleep is concerned (even if that means going to bed at midnight!), choosing a bedtime that’s 8 hours before you need to wake up helps ensure you get enough sleep.
• Keep your bedroom dark, quiet, and cool. Studies show that a cooler room (between 60-67°F) makes for better sleep, while trying to go to bed in a warm room impairs sleep.^[40]
• Use sleep aids, if needed. You may want to experiment with sleep aids like ear plugs, eye masks, or calming essential oils to help create a sleep-promoting environment.
• Remove electronic devices or screens from your sleeping area and bedtime ritual. Blue light from these screens mimics sunlight, which tricks your circadian rhythm into thinking it's day time—in turn making it harder to fall asleep at night. If limiting blue light exposure is difficult due to your living situation, wearing amber-colored glasses at night can help achieve a similar effect.^[41]
• Consider putting together a calming nighttime ritual. This can include any relaxing activities that work for you, such as reading or journaling, prepping clothes for the following day, using candlelight, or taking a warm bath. The idea is to create a peaceful environment and consistent nightly behaviors that contribute to better sleep.
• Choose pillows, blankets, and mattresses that promote maximum comfort. Being physically comfortable while you sleep goes a long way to support sleep quality!
• Address any unmanaged sleep disturbances, like sleep apnea. If you feel poorly rested each day despite going to bed and waking up at reasonable hours, consider seeing a doctor to rule out sleep disorders.

Rather than looking at this like yet another task to add to your endless to-do list, we can think about our sleep routine as a treat—a self-care practice that we get to create and enjoy every night.

Depending on our work schedules, childcare, or other responsibilities, we may have more or less time and control over our sleep hygiene. But there are always choices we can make that can either contribute to, or take away from, a good night's sleep.

Can you get too much sleep?

While insufficient sleep is regularly linked to a higher risk of chronic disease and mortality, excessive sleep (more than 8 or 9 hours per night) also shows some associations with health risks in observational studies.^[42]

However, this doesn’t mean that allowing your body the rest it craves is a problem! Rather, so-called excessive sleep seems to be a marker for other existing health issues, including depression, undiagnosed sleep disturbances (like sleep apnea), immune problems, and illnesses that increase the body’s sleep needs.^[43]

If you find yourself sleeping for unusually long periods each night, consult your physician to rule out any underlying health conditions.

The bottom line

In our modern culture that prizes working more and resting less, it can be hard to prioritize sleep over things like exercise.

But if you’re getting up early (against your body's natural inclination) or staying up late (while feeling “wired but tired”), you may be inadvertently sabotaging your health, as a lack of sleep can hinder the very things you're looking to improve through other health-promoting activities.

So, the verdict is in: prioritizing sleep can dramatically improve your health and life, especially when combined with other foundational health practices like eating a nutrient-dense diet and strength training. Are there any sleep hygiene tips we missed? Let us know!

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