Correlation between sleep and body weight (the science explained)


I can’t be the only one that loves sleep, right?

Like, give me a snacks in bed and an 8pm bedtime on a Friday night over packed bars and 2am Uber rides.

I know everyone isn’t as lame/boring as I am, but I hope the other 5 nights of the week you are getting adequate sleep.

Not because I also want you to be boring, but because sleep is crucial for our health and well being.

If you need 3-4 cups of coffee per day just to “function”, then you need to take a closer look at your sleep hygiene.

There is a direct correlation between the quality of our sleep and our body weight.

But how? And why? And how do you fix it?

Well – let’s get into it and take a closer look at the importance of sleep on body weight.

What is Quality Sleep

Why is it that sleep is always the first thing to go when we are pressed for time?

We think of sleep as some sort of luxury, like we are LUCKY to get 8 hours of sleep, when in reality we should be getting 8 hours of sleep regardless.

The importance of sleep goes far beyond just “not feeling tired”.

There are two different “types” of sleep we get; NREM (non-rapid eye movement) and REM (rapid eye movement).

About 75-80% of our sleep is in the NREM cycle. NREM is the deepest sleep we get and is essential for transferring short term memories to long term memories and is the point when our growth hormone release is highest (which is important for cell renewal and repair).

REM sleep is when we have rapid eye movement and when we do most of our dreaming.

It is also when we have the most movement, activity, rapid heart rate and faster breathing.

Some scientists go as far to say that REM sleep is a place for our brain to deal with emotional situations we might not encounter on a daily basis.

There are actually 5 different phases of sleep cycles we go through, and they start over every 90-110 minutes!

Sleep is important for people of all ages as it is like a “reset”.

Imagine your phone. You plug your phone in to charge every night. If you don’t plug it in, it starts to slow down and eventually it just shuts off and you cannot use it until you charge it up again.

The same goes for our bodies.

If we do not get enough sleep, we cannot fully function to the best of our ability.

We also cannot complete all of the body process’ that occur when we sleep like muscle repair, cell regeneration, hormone releases and more!

How Much Sleep Do we Need

Generally speaking, adults need anywhere from 7-9 hours of sleep (sometimes more).

This is specific to each individual based on their lifestyle.

If we move more during the day and exert ourselves, we likely need more sleep to recover.

If we lay around all day with minimal movement, we likely need less.

We also know that when there is a traumatic event, illness, loss of sleep in previous days we are going to need more sleep to “catch up” and help to recover quicker.

Sleep and Weight Loss

Sleep is directly correlated to metabolism/hormone health.

If you are not getting adequate sleep, your body is automatically going to down regulate your hormones and leave you in a tornado of imbalances and issues.

A research study published by Annals of Internal Medicine looked at two groups of individuals with the same training routine and calorie intake and altered their sleep schedules.

One group slept for 5.5 hours per night while the other slept for 8.5.

The results were intense! The group with more sleep actually lost more fat than the group who slept less.

Not to mention those who slept less actually lost 60% more muscle than those who slept more (this is because the body wanted to preserve the fat for energy and got rid of the muscle)!

This is again, from the metabolism down regulating. What this means is that our metabolism slows down during the day to preserve energy.

So, the truth is,  we all think it’s the moving and exercising that burns more fat, but really it is when we are in a state of homeostasis.

Why Is Sleep Important for Weight Loss

In order for the body to lose fat (or weight) it needs to feel “safe”.

This means it needs to have manageable stress, exercise, healthy foods, water…the perfect storm.

If stress is high, the body is going to release stress hormones that tend to inhibit fat loss.

Sleeping lowers stress levels naturally, it is your bodies way of recharging, as I said earlier.

Imagine this…you are eating less food than the body needs (dieting), you aren’t sleeping well, you are only drinking 40 ounces of water per day, your stress with work and kids is through the roof…and you can’t figure out why you are sluggish and can’t lose weight.

Do you think the body feels safe? Do you think it is in a state where it would be willing do something for you even though you aren’t supporting it?

Likely no.

Aside from stress, there are other reasons sleep is important for weight loss.

For instance, individuals who sleep less have a tendency to create more of the appetite stimulating hormone ghrelin.

This hormone sends a signal to the brain that you are hungry, when in reality, you are not.

This causes individuals who sleep less to actually OVER EAT and, not to mention, they tend to crave foods that aren’t as nutritious for our bodies like processed carbohydrates and trans fats.

Are we starting to see trends here? Let’s take a look at sleep deprivation.

Negative Effects of Sleep Deprivation

Sleep deprivation is an official term for that zombie feeling after a night of zero sleep.

Not to be confused with insomnia – insomnia is when people have enough time to sleep and can’t. Whereas sleep deprivation is usually less time allocated towards sleep due to lifestyle choice or obligations.

There are also other terms in the sleep science world..

Sleep insufficiency (or deficiency) is when you may have been in bed for the length of time necessary, but you aren’t getting deep sleep or you are waking up several times.

Both are going to cause the same negative effects because lack of sleep is…still lack of sleep.

Let’s talk about the negative effects of sleep deprivation, both short term (acute) and long term (chronic).

Acute sleep deprivation can lead to drowsy-ness, inability to concentrate, slow reaction time, mood changes, cravings, know, all the things you experience when you get 2 hours of sleep after a late flight or night out.

Chronic sleep deprivation can lead to many more serious health concerns – things like cardiovascular disease, diabetes, obesity, compromised immune system, mental health disorders, hormone abnormalities and more.

Sleep effects every single body function and process, so without it, everything starts to see the effects.

Signs of Sleep Deprivation

There are some warning signs you can look at for sleep depravation.

My thought – you likely know when you are not getting enough sleep. Could be a job, family, travel, new baby..several different factors.

But what is important to note is that whatever it is, it needs to be temporary. Because long term sleep depravation can lead to that laundry list of complications I listed above.

But – incase you want to check your habits with the science, signs of sleep depravation include:

slowed/delayed thinking

reduced attention span’

poor memory, unable to remember things

risky decision-making, recklessness

lack of energy

mood changes – feelings of stress, anxiety, irritability, anger etc.

Sleep and over all health

Sleep is not only important for fat loss and reaching our fitness goals, but it is also important for overall health!

Researchers are now saying that getting enough high-quality sleep is just as important on health as a good diet and exercise program.

We do not just wake up one day with heart disease or obesity, they are caused by poor habits adding up over time.

I am a HUGE advocate of diet and lifestyle changes being NUMBER ONE importance when it comes to decreasing chronic disease and healthcare costs.

Just because something you eat today doesn’t feel like it is harming you, adding that up day after day for a course of multiple years is where we run into problems.

Studies on insufficient sleep have been linked to health concerns like:

Obesity (since we talked about fat loss above)

◊ Diabetes (because lack of sleep can cause an imbalance in hormones and lead to insulin sensitivity/resistance)

◊ Cardiovascular disease/Hypertension/Heart Attack (these can be caused by the body not having enough time to “reset” and therefore leading to extra stress on the body)

◊ Immune function (lack of sleep has been shown to cause inflammation and decrease the ability to resist infection) This also goes hand in hand with getting sick more frequently.

◊ Hormone health (lack of sleep can cause hormone issues, especially adrenal fatigue)


So did we learn that sleep is crucial for weight loss and that there is an absolute correlation between sleep and your bodies ability to lose fat?

I hope you answered YES!

Next time you are wanting to lose weight, think about sleep and decreasing stress before you start worrying about what needs to be taken from your diet or your lifestyle. Focus on the easy habits FIRST, then you can start to refine from there.

And don’t forget, eating too close to bed can lead to sleep disruptions because digestion is working so hard. Something to think about!

If this blog was helpful for you I ask that you share it on social media! The best way to grow a small business like this is through social sharing and word of mouth.

I appreciate you taking the time to read, see you next time!

Haley Rowe January 4, 2022