What a Lack of Sleep Does to Your Hormones and Your Love Handles

Jonas Salzgeber
May 26, 2016 · 9 min read

By Jonas Salzgeber — Previously published on my brother’s and my life blog.

Sleep plays a major role when it comes to EVERYTHING. Including losing weight. Yes, losing weight is not only about the right exercise regimen and a healthy diet but also about getting enough high-quality sleep.

Let’s learn why.

A Lack of Sleep Makes People Fat

The claim is clear:

Sleep less → weigh more.

And science backs this up:

  • This American study looked at 68,183 women over a period of 16 years. Conclusion? Sleep 7 hours and you’re fine, sleep 6 hours and you gain weight, sleep 5 or less hours and you gain more weight. [1]
  • This study in Japan looked at 35,247 employees (mostly men) and concluded that “short sleep duration was associated with weight gain and the development of obesity over 1 year in men.” [2]
  • Another American sleep study stated that losing just 16 minutes of sleep per night increased the risk of obesity. [3]
  • In a Stanford University study they looked at relationship between 1024 people’s sleeping habits and their weight. The data revealed that sleeping less than 8 hours was associated with obesity. [4]

In short: A lack of sleep makes people fatter. That’s what the research of thousands of people tells us. (I’m well aware that sleep is only one of many factors that contribute to a healthy lifestyle & weight.)

So, why does a lack of sleep make people fatter?

Here’s a plausible reason.

A Lack of Sleep Makes You Crave More Snacks

Oh yeah.

A sleepy man can’t resist some M&Ms…

Research backs this up. (Read the studies, it’s eye-opening.)

  • People were allowed to sleep 5.5 hours on one night and 8.5 hours on another and then measured how many FREE SNACKS they downed the next day. On less sleep they ate 221 calories more → if you get too little sleep every day that’s some nasty weight gain due to snacking… [5]
  • The same study stated that the increased snack intake happened between 11pm and 7am… That’s when you could (or should?) be asleep.
  • Haha, this is a fun Swedish study: Grocery shopping on 2 days, once sleep deprived and once after a normal night of sleep. Guess what, sleep deprived grocery shopping ended up with significantly more junk food… [6]
  • In this study they stated that less than 6 hours of sleep resulted in an increase in appetite for high sugar foods. [7]

Apparently, if you don’t sleep enough, you crave more crap food. You eat more crap food but you also buy more crap food… So, never go grocery shopping on too little sleep.

Interesting, right?

Now, why does a lack of sleep makes you crave more food?

Because of your hormones. (Yes, this is also true for MEN. We have hormones, too… ;-) )

Your Hormones Go NUTS on Too Little Sleep

First of all, what are hormones anyway?

Hormones are chemical messengers in your body. I like how the sleep doctor Dr. Michael Breus puts it:

“Hormones act like traffic signs and signals by telling your body what to do and when and making sure its machinery runs smoothly and maintains homeostasis, or balance.”

Cool, huh?

Now the claim is that a lack of sleep makes your hormones, or traffic signs, go nuts so that your body gets off balance.

We’ll look at 5 hormones that are affected by sleep and influence weight gain — insulin, ghrelin, leptin, cortisol, and growth hormone.

(Pssst… Here’s one more thing: I don’t think that hormones go nuts on too little sleep, that’s just the natural way our body responds to a lack of sleep. Naturally, we would only deprive us of sleep in emergency cases, and the following reaction of the hormones would actually help us survive and not make us fat.)

Insulin: Makes You Store Fat

No, insulin is not just the diabetes hormone.

Insulin is your major fat-storing hormone (and it’s darn important for survival).

In short: When you have more insulin, you store more fat.

Naturally, insulin reacts to carbohydrates. But if you don’t get enough sleep, you become temporarily insulin resistant. [8] And guess what, this again leads to weight gain. [9]

​It’s easy: If you don’t get enough sleep you become temporarily less sensitive to insulin. This lets you produce more insulin. A higher insulin level makes you store more fat. And more stored fat means more weight.

Ghrelin & Leptin: The Remote Control for Your Hunger and Appetite

Remote control… Cool idea. But it’s not mine, I stole it from Dr. Michael Breus’ book The Sleep Doctor’s Diet Plan.

Here’s what he says:

Two hormones, ghrelin and leptin, hold the remote control for your appetite. Ghrelin is the green light that says, “Go get some food!” Leptin is the red light that says, “Stop eating now!” — Dr. Michael Breus

Now, what happens if you get too little sleep?

In short: Too short nights lower the level of leptin and boost the production of ghrelin → you’re hungrier all day long.

There are different studies that back this up. [10] [11] Sleep less than 6.5 hours and you end up hungrier because of these hormones. Plus it’s even a negative correlation, which means, the less sleep you get, the higher is the production of the hunger hormone ghrelin… Sleep less, be hungrier.

That’s bad news for people who want to lose weight and get too little sleep… It’s just so much harder, if not impossible, to lose weight. It’s hard to fight against the own body. Because the body truly believes you’re hungry even if you’re full. (Naturally you need more energy if you’re sleep deprived, that explains the reaction of your hormones.)

That sucks. But it explains a lot.

Cortisol: Causes You to Break Down Muscles for Energy…

You’ve probably heard it before: Stress causes your body to produce cortisol.


Because if you’re stressed you need additional energy to cope with whatever you’re facing — a tiger, a fight with your arch-enemy, or, more likely, a lot of work…

As you need extra energy, you need the hormone cortisol that converts stored energy into usable energy. So naturally, cortisol is super helpful and helps you be wide awake in the right moments…

So stress increases cortisol. You know what else also increases cortisol production?

Right, a lack of sleep.

Lack of sleep increases cortisol production, making you store fat and burn muscle. A high cortisol level also increases your appetite. — Dr. Michael Breus

This sucks a ton. Except if you want to lose lean muscle, gain fat, and crave more food…

Human Growth Hormone

You definitely want a lot of Human Growth Hormone (HGH). This is the stay young, slim & sexy hormone.

And guess what, HGH production is highest during deep sleep.

If you get less sleep, you automatically have less deep sleep, and therefore less HGH… simple as ABC.

What does HGH do anyway?

HGH decreases the rate at which your cells utilize carbs and increases the rate at which they use fats → great if you want to lose fat.

Poor sleep reduces HGH. That in turn increases the storage of fat…

That’s just how it is.

So, if you want to stay young, slim & sexy → get enough sleep.

Lack of Sleep Leads to Unbalanced Hormones

Hormones dictate many of our body’s functions. And adequate sleep balances our hormones.

In other words: Too little sleep makes your hormones get out of balance.

Here’s again what happens with your hormones if you don’t get enough sleep:

  • Insulin is increased (due to short-term insulin resistance) so you store more fat.
  • Leptin is reduced so you eat more because there’s nothing telling you to stop.
  • Ghrelin is increased so you eat more because it’s telling you to do so.
  • Cortisol is increased so you eat more and use muscles for energy.
  • Human Growth Hormone is reduced so you store more glucose as fat.

Put together: a lack of sleep makes you more likely to gain weight rather than to lose weight. You simply stack conditions against you.

“But I know of a friend who lost weight on a diet and didn’t sleep more than 5.5 hours a night.”

Your friend probably lost lean muscle mass…

Lost Weight on too Little Sleep? Maybe You Lost Muscles…

This is a fascinating study with dieters. [12]

Group 1: Put on a diet, 8.5 hours of sleep

Group 2: Put on the same diet, 5.5 hours of sleep

Now, what happened?

Interestingly enough, both groups lost the same amount of weight… Group 1 lost fat and group 2 lost lean body mass (aka muscle mass). That’s one point for more sleep. Another point for more sleep is that group 2 claimed to be much hungrier (no surprise, huh?) which made it harder to stay on the diet.

The take-away: Get more sleep.

And one super easy way to do that is to replace one hour of TV with one hour of sleep. This simple change could result in substantial weight loss over time. This study suggests that swapping one hour of TV for sleep could result in a loss of more than 14 pounds a year… [13]

Sleep Deprivation: The Royal Route to Obesity

That term is stolen from sleep research specialist Eve Van Cauter.

Don’t get enough sleep and you’re on the royal route to obesity…

LOVE that term. And now that you’ve read the article you know it’s true.

Quick recap: If we get too little sleep our hormones play against us. The odds are against us. It’s simple: Too little sleep is the royal route to obesity…

Get this (it stars HULK):

You see, it isn’t always about willpower. So many amazing and strong people fail at weight loss because they’ve unknowingly stacked conditions against themselves. By being sleep deprived, your inner incredible hulk highjacks your brain and you can’t resist doing the very activity that you promised yourself not to do. — Shawn Stevenson

AWESOME! Your inner incredible hulk…

This is so true.

No wonder a sleepy man can’t resist M&Ms… Hulk wants them so badly.

What’s the solution?


The research is clear and conclusive: Giving your body the rest it needs will enable you to lose weight even if you do not alter your diet or fitness routine. Furthermore, no matter how conscientious you are about what you eat and how active you are, a poor sleep pattern is likely to torpedo your good intentions and allow those extra pounds to creep onto your body and stay there! — Dr. Michael Breus

One Last Thing…

Being overweight or obese is a double-edged sword. Not only does obesity contribute to sleep problems, but sleep problems can also contribute to obesity. — Shawn Stevenson from Sleep Smarter

We learned that a lack of sleep definitely can make you gain fat. Now, if you’ve gained a lot of fat (for whatever reasons) you maybe don’t sleep well. And that again can make you gain more weight. It’s a vicious cycle.

So if you sleep well, you might just want to get more sleep.

If you don’t sleep well, you might want to check out my article on lifestyle-sleep mistakes which can help you fix your sleep. And after that you can get more sleep. :-)

(If you have serious sleep disorders you want to check with your doctor.)

That’s it — sleep is super-duper important when it comes to your weight. And you now know what roles your hormones play. They play a key role.

Thanks for reading. If you’ve learned something in this article (remember ghrelin?) then show some and spread the word. I appreciate it.

FREE PDF: Learn the exact steps to fall asleep faster

Trouble falling asleep?

We put together a step by step checklist that possibly helps you fall asleep faster at night. Give it a try and get over tossing & turning… it’s free for now.

Jonas Salzgeber

Written by

Author of The Little Book of Stoicism and blogger specializing in the application of Stoic philosophy & co-founder of www.njlifehacks.com

Welcome to a place where words matter. On Medium, smart voices and original ideas take center stage - with no ads in sight. Watch
Follow all the topics you care about, and we’ll deliver the best stories for you to your homepage and inbox. Explore
Get unlimited access to the best stories on Medium — and support writers while you’re at it. Just $5/month. Upgrade