How Many Calories Do You Burn in Your Sleep?

If there’s one thing most of us can agree on, it’s that sleep is one of life’s greatest pleasures. There’s nothing quite like collapsing into bed after a long day, pulling the duvet up to your chin, and drifting off. But while you’re snoozing away, your body is actually surprisingly busy. In fact, you’re burning calories – even though you’re doing what looks like absolutely nothing. 

But how many calories do you really burn in your sleep? And is it enough to make any noticeable difference? Let’s dive into the surprisingly fascinating science behind nighttime calorie-burning. In this guide, we’ll explain why it varies from person to person and what you can do to maximise (a little) of the metabolic magic that happens while you’re in the land of nod. 

Your body doesn’t switch off (even when you do) 

It’s easy to think of sleep as a time when everything shuts down, but that’s not actually the case. When you’re asleep, your body is still hard at work performing all the essential behind-the-scenes tasks that keep you alive and functioning. These include: 

• Breathing and heart function 
• Repairing cells and tissues 
• Regulating hormones 
• Consolidating memories 
• Balancing immune function 

All of this maintenance requires energy and energy means calories. So even if you feel like a lazy potato in bed, your body is quietly running a full-on night shift. 

How many calories do you burn while sleeping? 

Here’s the bit you came for. 

On average, a person burns around 0.9 calories per kilogram of body weight per hour while sleeping. (If you prefer stones and pounds, don’t worry – we’ll break it down.) 

Let’s say you weigh 70 kg (around 11 stone). The calculation looks like this: 

70 kg × 0.9 calories × 8 hours of sleep = 504 calories 

Not too bad, eh? 

But this is just an average. The actual number can vary based on: 

• Weight 
• Age 
• Metabolic rate 
• Gender 
• Sleep quality 
• Body composition 

Some people burn fewer calories; others burn more. If you’re younger, more muscular, or have a naturally faster metabolism, your nighttime calorie burn tends to be higher. If you’re older or your metabolism has slowed down a bit (as happens to most of us at some point), it’ll be a bit lower. 

Why muscle mass matters (even when you’re asleep) 

If you’ve ever heard someone say “muscle burns more calories than fat,” they weren’t lying; and this applies even during sleep. 

Muscle tissue is metabolically active, meaning it requires energy simply to maintain itself. Fat tissue, on the other hand, is more like storage – it doesn’t need much energy to just sit there (1). 

So, if you’ve been doing resistance training, strength workouts, Pilates, or anything that builds muscle, you’re very likely burning more calories at night than someone with less muscle mass. You essentially get a little bonus burn for all your hard work during the day. 

Your brain burns more calories than you think 

It might not feel like it when you wake up feeling groggy and confused, but your brain is incredibly active at night. In fact, your brain uses about 20% of your total daily energy, even though it represents only a small percentage of your body weight. 

During sleep, the brain: 

• Processes the day’s events 
• Forms new memories 
• Clears out waste chemicals 
• Regulates emotions 

All of this takes energy. Some research even suggests that dreaming phases (REM sleep) burn more calories because your brain activity spikes (2). 

So, the next time someone calls you lazy for sleeping in, why not tell them your brain is doing loads of heavy lifting? 

Can improving your sleep increase how many calories you burn? 

Surprisingly yes, but only slightly. Good-quality sleep improves your metabolic rate, while poor sleep does the opposite. 

Here’s how: 

1. Deep sleep boosts fat-burning 

During deep sleep, your body releases growth hormone, which helps repair muscle and burn fat. If you’re tossing and turning, you spend less time in this restorative stage (3). 

2. Poor sleep slows your metabolism 

Studies show that consistently bad sleep can cause your metabolism to drop, making you burn fewer calories both day and night (4). 

3. Bad sleep increases appetite 

Ever noticed you’re ravenous after a late night? That’s because lack of sleep increases ghrelin (the “I’m starving” hormone) and reduces leptin (the “I’m full” hormone) (5). 

So, even though sleeping more won’t make you burn hundreds more calories, good sleep does support a healthier metabolism overall. 

What affects how many calories you burn in your sleep? 

When it comes to burning calories while sleeping, here are the main factors: 

• Body size: Heavier people burn more because the body has more mass to maintain. 
• Muscle mass: More muscle = more calorie burn. 
• Age: Younger bodies have faster metabolisms (6). 
• Sex: Men tend to burn slightly more because they generally have more muscle (7). 
• Temperature: A cooler room can make your body work harder to maintain its core temperature (8). 
• Health conditions: Thyroid function, medications, and hormone levels can all make a difference (9). 

So, if your friend claims they burn 700 calories a night while you burn 450, it’s not a competition; it’s just biology doing its thing. 

Should you try to lose weight while sleeping? 

It would be brilliant if we could lose a noticeable amount of weight just by going to bed earlier. Sadly, snoozing alone won’t give you dramatic results. 

Eight hours of sleep will burn a handful of calories, but not enough to replace healthy eating or exercise. That said, sleep is still a massively underrated part of weight management. Better sleep can: 

• reduce cravings 
• improve mood (which helps with motivation) 
• support muscle recovery 
• balance hunger hormones 
• boost daytime energy, making you more likely to be active 

While sleep won’t magically melt fat, it does create the ideal environment for fat loss to happen when combined with a balanced lifestyle. 

How to maximise your night-time calorie burn (gently) 

You can’t hack your sleep to burn hundreds more calories, but you can optimise your metabolism in these simple, sustainable ways: 

1. Build muscle: Even two short strength sessions a week can make a difference. 
2. Keep your bedroom cool: Around 18°C is ideal for slightly boosting calorie burn and improving sleep quality. 
3. Prioritise deep sleep: Reduce screen time before bed, avoid heavy meals late, and develop a calming routine. 
4. Move more during the day: The more active you are overall, the higher your resting (and sleeping) metabolic rate becomes. 
5. Eat enough protein: Protein supports muscle maintenance, which supports calorie burn (10). 

Final thoughts: you burn more calories than you think 

So, how many calories do you burn in your sleep? For most people, somewhere around 350–550 calories over eight hours. It’s not enough to dramatically change your weight on its own, but it’s still a satisfying reminder that your body is doing valuable work even when you’re not conscious. 

Think of it this way: sleep isn’t a weight-loss strategy, but it is an essential part of a healthy lifestyle. And if the idea of burning calories while being tucked up in bed motivates you to prioritise sleep – that’s a win all round. 

Sources: 

1. https://www.massgeneral.org/news/article/why-muscle-mass-matters-and-how-to-keep-it 

2. https://www.sleepfoundation.org/how-sleep-works/how-your-body-uses-calories-while-you-sleep 

3. https://pmc.ncbi.nlm.nih.gov/articles/PMC2929498/ 

4. https://www.sleepfoundation.org/physical-health/weight-loss-and-sleep 

5. https://pubmed.ncbi.nlm.nih.gov/18564298/ 

6. https://www.healthline.com/nutrition/metabolism-and-age  

7. https://www.cambridge.org/core/journals/british-journal-of-nutrition/article/is-resting-metabolic-rate-different-between-men-and-women/9C459AF222731088FD876D608B5228D9 

8. https://www.bbc.co.uk/news/health-63602501 

9. https://www.uclahealth.org/news/article/surprising-connection-between-sleep-and-weight-management 

10. https://www.betterhealth.vic.gov.au/health/healthyliving/protein