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How Sleeping Too Little May Hinder Weight Loss

Updated: Jul 19, 2022

Stress and the demands of everyday living have us all trimming the edges to stay on track. We skip our exercise, sleep less, grab food on the run, all in an effort to keep up with the hectic pace of living. I definitely have plenty of first hand experience of the impact of lack of sleep on hunger, cravings and food choices! Now it all makes sense.

With so much going on, cutting back from the recommended (and required) seven to nine hours of sleep might seem like the answer. I mean, if you only sleep six hours, that gives you two more hours to be productive, right?!

Well, not really. And while it seems like sleeping less might be a good solution to the time crunch vs. ab crunch conundrum (or other exercise of your choice), here’s why cutting back on sleep just won’t work.

First off, your brain is TIRED when you don’t sleep.

You‘re operating in a fog and making the best decisions is pretty much impossible. When you stop by the coffee shop, nine times out of ten, you will grab the donut to go with your coffee because you're so depleted you THINK you really need the one-two punch of sugar and caffeine to get you going. Your brain’s reward centres are revved up from lack of sleep and your food cravings are in overdrive. Do you see where this is going? That’s right. Straight to your hips, not to mention the sugar spike and inevitable crash that comes later, all making things that much worse.

Studies consistently show us that when our bodies are starved of sleep we opt for quick-fix, high-energy (often ultra-processed) snacks in an effort to keep going. A study at the University of Chicago even showed that participants who slept less than eight hours chose snacks with twice the fat content compared to their well-rested counterparts. Higher brain functions may also be reduced, which are vital for making good food choices, so those deeper brain functions that react to basic desire are the ones which end up in charge! Uh-oh!

Second, crappy choices, bigger portions, and no impulse control in the kitchen are bound to produce weight gain, but in addition to changing how your brain functions, sleep deprivation has a powerful effect on hormone production.

Cortisol, leptin, and ghrelin, which may sound like goblins from the Lord of the Rings, are really the three hormones most commonly connected to weight control. Although we mustn't forget insulin either!


Cortisol is your stress hormone and it suppresses your metabolism. It’s produced by your adrenal glands, and if you aren’t well rested it’s a safe bet that your stress levels are going to be elevated. Cortisol tells your body to save its energy and that means it’s going to hang on to fat. The jury is still out on whether cortisol has a direct bearing on weight loss, but for anyone with emotional eating habits, higher cortisol levels are potentially a recipe for disaster. Stress makes us seek comfort and for many of us, food is a go-to for feeling better.

As another little aside, because cortisol is produced by the adrenal glands and this is also where oestrogen is produced once we hit menopausal years and oestrogen production in the ovaries drops off, if we're chronically stressed then cortisol release takes precedence. This may lead to increased abdominal (tummy) fat! So, working on stress management can be really helpful.


Leptin is a hormone produced in your fat cells. It tells your body when to stop eating and to burn more calories. When you are tired, your body produces less leptin so your appetite is out of control and your metabolism slides into low gear. Not being able to recognise our body’s hunger signals is difficult enough without the added magic of hormones confusing our wants and needs.


Ghrelin is a hormone released by your stomach that makes you hungrier, slows down your metabolism, and decreases your body’s ability to burn fat. When you are sleep deprived, your body makes more grehlin. Awesome. That means you are tired, want to eat a whole lot of garbage, and aren’t programmed to burn it off. Lack of sleep has been tied to increased levels of ghrelin in countless studies. I think of it as the number one gremlin!


Finally, as if all that hormonal turmoil wasn’t enough, four days of poor sleeping have been proven to be enough to hamper your body’s ability to process insulin too. Insulin is the hormone that your body uses to convert food, particularly sugar and starch, into energy. In one study, all it took was four days of sleeping too little to reduce the body’s insulin sensitivity by 30%. Poor sleep can impair glucose tolerance and lead to insulin resistance and obesity

Research shows time and time again that poor sleep, and less sleep (under seven hours typically) can have a highly detrimental effect on weight loss efforts, and overall health. If you aren’t sleeping enough, you are destabilising your own metabolism, your internal sensors and your hunger hormones, and that’s going to make you (or keep you) an unhealthy weight. This is why I always talk to clients about their sleep, often looking at sleep-wake cycles and sometimes suggest keeping a detailed sleep log, which we can then explore and work on. This can sometimes have one of the most profound effects on wellbeing, health and weight management. This is actually something I've been personally working on for the last six months (no, Rome wasn't built in a day) for general health and wellbeing, and it's so worth it!

As an aside, it's probably also worth mentioning that regularly sleeping too much can also be detrimental to overall health, although possibly not as much as under sleeping. If you struggle to get up and are regularly spending more time asleep than nine hours, it may be worth exploring why you think that is, and maybe worth also discussing with your health care provider.

Set yourself up for success with a bedtime routine. Most of us know that we perform better when we are well rested. That’s why we usually strive to get some quality sleep before a really big day. When you are embarking on a weight loss plan, you’ve got to use that kind of good sense and self-care. Put away your electronics, relax, and create a bedtime ritual that will help you nod off because the time you spend snoozing is just as important as the time you spend meal prepping and getting moving. They're all pieces to the healthy weight puzzle!

It’s all about self-care. Every day.

That’s how you’re going to succeed at weight loss and maintaining a healthy weight, whatever that may look or feel like for you.

Small changes, consistent positive habits, big rewards!

Look out for my upcoming blog on ways to improve your sleep. Or if you want to get in touch just email me at

Please note: This article is intended to be for educational purposes only, and does not constitute medical advice or replace professional assessment or personalised advice.

I do not hold responsibility for the information on any links to external websites within this article and information within these links/websites may change at any time or no longer be accessible. Any website pages/links added are also for education purposes only.

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