If you’ve ever turned in at 2 A.M. the night before an early meeting, you know how inadequate sleep affects your day. Your energy levels are low, you can’t think straight, and all you want to do is crawl back into bed.
But irregular sleeping habits impact more than just your mood. Weight loss, sleep, and overall health are all intimately connected, and there’s evidence to suggest that sleep deprivation has a negative effect on your metabolism. Plus, a lack of sleep is one of the many causes of weight gain.
So, let’s take a deep dive into the correlation between metabolism and sleep (or a lack thereof).
Most of us have probably heard a friend say, “I’m so thankful for my fast metabolism—I can eat anything I want.”
But what exactly does that mean? And is there any truth to such a claim? Before we jump into the science behind good sleep and metabolism, it’s essential to understand what metabolism is.
Anytime you eat or drink something, your body converts it into energy.
This process of converting calories from food or drink into energy is called metabolizing.
Your metabolism, then, is your body burning fuel to keep you alive.
Even at a standstill, your body burns calories to complete basic functions like pumping blood and breathing. The expenditure of energy for these survival functions is your basal metabolic rate (also called your resting metabolic rate).
This metabolic rate varies among individuals, depending on weight, sex, age, body composition, and other factors.
Ultimately, a “fast” metabolism burns calories quicker than a “slow” one.
Your body weight and your metabolism are linked. Simply put, if your metabolism burns more calories than you consume, you can lose weight (though this isn’t the only factor involved in weight loss).
While the jury is still out on the exact mechanisms behind sleep’s effect on metabolism, a growing number of studies have shown that there is indeed a link between the two.
One study of 14 healthy men found that even a single sleepless night impairs the body’s metabolic rate.
After a 24-hour period of wakefulness, the subjects were found to have a reduced energy expenditure. Their bodies were conserving energy—or, to put it another way, their basal metabolic rates slowed down.
Another study of 36 adults came to a similar conclusion.
Instead of one 24-hour period without adequate sleep, subjects were made to sleep four hours per night for five nights, then given a 12-hour recovery sleep. The results showed a decrease in resting metabolic rate of around 2.5%. After the lengthy recovery sleep, these numbers returned to normal levels.
These studies—and others like them—suggest that restful sleep plays a vital role in overall well-being, especially when it comes to your metabolism. If you regularly miss out on sleep, wake up several times in the middle of the night, or pull all-nighters, your body is likely to slow the rate at which it burns energy.
But sleep deprivation affects more than the number of calories you burn. There are microscopic changes that take place at the hormonal level.
Because the term “metabolism” refers to a whole range of bodily chemical processes, there’s value in addressing some of the individual hormones at play when it comes to sleep deprivation.
Remember the first study we mentioned? The researchers found that several hormones spiked after the sleepless night. One such hormone was cortisol.
Ever wondered about how stress and weight gain are related? Cortisol is the body’s primary hormone when it comes to stress. There are many ways that stress contributes to hormonal weight gain, but in terms of sleep loss and metabolism, increased cortisol levels can cause your body to conserve energy.
Think of it as your body storing fuel for whatever stressful moment is coming up. As we know, the body should burn energy regularly—not store it.
Sometimes called the “hunger hormone,” ghrelin increases food intake.
The same study found an increase in ghrelin levels after a night without sleep, which can mean an increased appetite for energy-dense foods.
Perhaps more importantly, ghrelin is associated with our circadian rhythms—the natural processes that occur within the body on a roughly 24-hour cycle. If increased ghrelin levels negatively affect circadian rhythm, a lack of sleep could throw off your “internal clock.”
Sleep deprivation can also affect your body’s ability to process insulin.
The hormone insulin is vital in the process that converts sugar and other foods into usable energy.
If your body isn’t responding well to insulin, it will struggle to process fats from your bloodstream. Instead, the fats are stored in the body as fat cells.
The relationship between insulin sensitivity and a good night’s sleep is why poor sleep is often associated with diabetes.
On top of the direct effects that sleep fragmentation or deprivation have on your metabolism, there are other indirect effects.
Running on too little sleep can lead to
. For example, if you only slept a few hours the night before, you probably won’t want to cook up a nutritious breakfast. Instead, you might hit up a drive-through for a greasy fast food combo. Then, all the fats and sugars in the processed foods will slow your metabolism.
Similarly, a sleepless night may leave you feeling tired, causing you to
skip your visit to the gym
. Because muscle cells require more energy for maintenance than fat cells, those with more muscle will have an increased metabolism. If your lack of sleep causes you to miss out on exercise, you’ve lost a chance to build muscle, and therefore missed an opportunity to raise your basal metabolic rate.
The bottom line? Your sleep habits affect your metabolism in several ways, both directly and indirectly. If you are wondering how to restart your metabolism, there are many ways to do so.
One of the best ways to address the impact poor sleep has on your metabolism is to find the root of the problem. In other words, determine what’s causing your irregular sleep habits.
For some, it can be a scheduling issue. Shift work often leads to a varied sleep pattern, and a heavy workload can make it tempting to skip sleep and focus on projects instead of health. In these cases, it’s wise to see if there’s an opportunity to lighten your workload or find a different schedule.
Other issues related to lack of sleep can be harder to control. Afflictions such as narcolepsy and sleep apnea make quality sleep difficult to achieve, leading to metabolic issues. There’s a reason why conditions like sleep apnea and weight gain are often associated with each other. Conditions like these often require more than a simple schedule adjustment.
So, if you’re looking to keep your resting metabolic rate at normal levels, how much should you sleep each night?
According to the CDC, the amount of sleep you should strive for each night changes as you age. In the first five years of life, children should sleep anywhere from ten to 17 hours per day (including naps). The recommended sleep duration drops to 8–10 hours for teenagers.
For adults aged 18–60, the CDC advises “7 or more hours per night” and 7-8 hours once you reach 65 and above.
Of course, time in bed does not equal restful sleep. To reap all the metabolic benefits of a good night’s sleep, you need to have quality sleep. Signs of quality sleep include:
Falling asleep within 20 minutes of getting into bed
Sleeping for more than 85% of your time in bed
Feeling well-rested in the morning
Waking up only once—or not at all—during the night
If you find that you’re sleeping most of the night and still not feeling rested the next day, you may not be completing full REM cycles during the night. REM sleep is one of the four stages of the sleep cycle, and you need to go through all four of them for a night of truly restorative sleep.
Poor sleep quality can be indicative of insomnia, sleep apnea, narcolepsy, and other conditions, so it pays to consult a medical professional if you feel tired throughout the day.
As you can see, sleep is an essential factor when it comes to your health and well-being. A regular sleep schedule can help with your metabolic rate, hormone production, and mood.
Yet when it comes to weight loss sleep is only a piece of the wellness puzzle. For some, sleep is the missing ingredient in their weight loss journey. But with anywhere from 25–80% of your body weight being determined by genetics, more sleep probably won’t translate to effortless weight loss.
It’s simple enough to change your sleep schedule; changing your biology is another story. But it isn’t impossible. That’s what we do at Found.
Found offers a science-backed approach to weight care that's based on your unique biology, psychology, lifestyle and prescription medication needs. Members receiving medication plus behavior change support from Found lost at least 13% more weight, and in some cases up to 229% more, compared to people receiving the same medication in clinical studies. To start your journey with Found, take our quiz.