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How Sleep Affects Metabolic Health (& Vice Versa)

Think food and exercise are the only things that matter for your metabolism? Here’s why sleep is actually the foundation of metabolic health.

Key takeaways

  • sleep is the foundation of metabolic health
  • insulin resistance kicks in after only a couple hours of sleep loss[1]
  • losing sleep makes you hungrier and more prone to binge on glucose-spiking junk food[2]
  • hormonal changes after sleep loss make it harder to lose fat[13]

When it comes to metabolic health, we usually prioritize exercise and eating right—the things we can tangibly do to improve insulin sensitivity and blood glucose.

Sleep is an afterthought for us because we think of it as the absence of doing.

But IRL, sleep is the bedrock of excellent metabolic health. And no amount of kettlebell swings or fat bombs (or fasting) can undo a lack of it.

Today we’ll elucidate why sleep, this black sheep of health advice, should be your #1 metabolic health hack. And for all you doers, we’ll share action steps on how to get better sleep quality, too!

How sleep impacts your metabolic health

Life is stressful. It’s so stressful that we need a system for recovering from the day’s wear and tear just so that our brains and bodies can function.

And that system, of course, is sleep.

During sleep, the body’s metabolic rate declines as each cell takes as much of a break as it can.[3]  It’s during this respite that our cells and organelles (including the mitochondria) are renewed in the process of autophagy.[4]

Now imagine that you worked every day without a weekend or vacation. The blechk you’d feel is exactly what happens to mitochondria—the cell’s powerhouses—when they’re sleep deprived. And when the mitochondria aren’t functioning at top form, your metabolic health nosedives.

This is because mitochondria produce up to 95% of your cellular energy.[5]

More on mitochondria, sleep, and metabolic health

In an interview on Found My Fitness, Dr. Matthew Walker, neuroscience professor at UC Berkeley, explained that skipping out on sleep “just annihilates the balance of energy intake and energy expenditure.” He pointed to 10-year study on 70,000 nurses which showed that sleeping five hours or fewer is highly associated with diabetes and obesity.[6]

It seems that tired mitochondria just can’t make enough energy for vibrant health. And in lieu of producing adequate energy from our food, our bodies store the energy as metabolically unhealthy fat.[13]

How the mitochondria prevent issues like insulin resistance is complex. But one reason is that when they’re not operating at 100%, the body accumulates toxic fat particles that decrease insulin sensitivity—which increases blood sugar.[7]

A 2010 study on 9 healthy people showed that a single night of sleep deprivation led to a large decrease in glucose tolerance and insulin sensitivity.[8] Another study that restricted nightly sleep to four hours for a week showed metabolic declines to the point where participants could have been classified as pre-diabetic.[9]

That’s just one week of not sleeping enough!

In the second study, researchers noted how cortisol and fight-or-flight nervous system activity were higher in sleep-deprived people than in rested. So sleep and metabolic health isn't linked by just one pesky fat molecule, but by the entire autonomic nervous system, which controls our hormones.

Sleep loss is linked to metabolic hormones

Dr.Walker said that the endocrine system is profoundly altered during sleep loss due to the autonomic nervous system. We can see this borne out in the research, where hunger hormones, satiety hormones, and fat-burning hormones are all flipped on their heads after a poor night’s sleep.

Here’s a snapshot of how sleep loss can disrupt hormone health:

  • One night of sleep loss increases ghrelin, the hunger hormone[2]
  • Short sleep reduces leptin, the satiety and fat-regulating hormone[10]
  • Partial sleep loss increases cortisol, which makes cells insulin resistant[11]
  • Testosterone production ramps down in sleep-deprived men, which is associated with insulin resistance[12]
  • The hormonal changes during sleeplessness can prevent fat loss[13]

The bottom line here is that sleep affects the balance between your fight-or-flight and rest-and-digest nervous systems, which in turn affects your hormones. If you get enough quality sleep, your hormone profile will promote energy expenditure and insulin sensitivity. If you don’t get enough sleep—or even if you get too much*—your body will favor fat storage and disease.

 *Studies show that getting over nine hours of sleep is associated with just as many metabolic health problems as not sleeping enough.[6]

How to get better sleep quality for better metabolic health

Sleep is necessary, and getting enough quality sleep will amplify all your other dietary and lifestyle efforts. Here are some ways to help promote better rest.

1.  Write down your top 3-5 goals just before bed

A team of researchers concluded that writing down your top goals for five minutes before bed will help you fall asleep faster than even journaling about what you already have accomplished.[14]

The act of writing about your goals turns any intangible stress into real, actionable tasks. This helps your brain to let go of the stress and get to work subconsciously on how best to accomplish those tasks for a relaxed, productive day. 

2. Eliminate blue light at least two hours before bed

Shutting off blue light for two hours before bed has been scientifically demonstrated to improve sleep quality and reduce insomnia.[15] Ways to help reduce blue light exposure at night:

  • Wearing blue-light-blocking glasses
  • Shutting down electronic devices two hours before bed
  • Using blue-light-blocking apps or your computer’s night mode
  • Switching to LED light bulbs that shift to red after a certain time

3. Eat more fiber

In a study conducted on 26 healthy people, fiber was associated with significantly more deep sleep compared to processed foods.[17] Theories abound as to why—gut flora and post-biotics could be a big part. But it could just be that fiber is increasing glucose stability, which in turn promotes deep sleep.[16]

4. Cut out caffeine past 10:00 a.m.

For all of you who have to have an afternoon cup of coffee to make it through the day…that very cup could be the reason you can't get through the day without an afternoon cup of coffee.

Here's the deal:

  • the quarter life of coffee is 12 hours
  • this means that if your last cup of coffee was at noon, by 12:00 at night, it's like you've just had a quarter cup of coffee
  • and that caffeine will disrupt your sleep[18]

So choose decaf after 10:00 a.m.

5. Get control of your blood sugar

We want to get better quality sleep so that we can have better blood sugar. But actually, that solution works both ways. One can hack their way into better sleep with glucose management. Blood sugar spikes are very stressful to the body. And the stress of continually elevated blood sugar is associated with poorer sleep quality and duration. [16]

The solution is threefold:

  • eat fewer meals per day and snack less—reduces insulin load
  • buy and cook real foods that have come out of the ground; and if it comes from a box, make sure it’s the highest quality, most blood-sugar friendly possible
  • and eliminate foods that spike your blood sugar

6. Learn how your body responds to food, sleep, & other lifestyle habits

To see how sleep affects your blood sugar in real time (and over time), we recommend using the Veri continuous glucose monitoring app. It’s the best way to see how your food is affecting your glucose, to see how sleep is affecting your glucose, and to manage your insulin and blood sugar for vibrant health.



Get started with Veri today


Further reading