Effect of Sleep on Metabolism
Next week, we will be releasing our Sleep
Foundations article, which we are excited to share with you (like our free nutrition foundations mega-article). This week, we will provide you with a taste as to how sleep and metabolism interact!
We discussed metabolism in the article on diet, so I won’t bore you with a discussion of the basics here. Well, sleep does actually influence our metabolism pretty profoundly. It impacts both our calorie expenditure
(calories out) and our calorie intake (calories in). When you sleep less, you end up burning fewer calories during the day at a baseline. Poor sleep results in disturbed hormones, notably thyroid hormones. Lower thyroid output leads to a lower metabolic rate. However, the bigger effect is likely due to the simple fact that being tired likely reduces your energy expenditure by reducing your output during training and your daily life (reduced exercise activity thermogenesis (EAT) and non-exercise
activity thermogenesis (NEAT)). Now, the overall impact may not ultimately add up to much, but it is important to realise that your metabolism and calorie expenditure is likely a little bit lower if you are sleep deprived. The effect could be quite large though, especially if sleep deprivation frequently leads to training being skipped due to tiredness or daily NEAT (as measured by steps for example) being very low.
A bigger effect of poor sleep seems to be its effects on influencing your calorie intake. Poor sleep is associated with an increased energy intake (calories in). Most of you have likely experienced this, where you get a poor night of sleep and you just can’t seem to feel full and you are just constantly hungry all day as
a result. This is quite common and obviously feeling excessively hungry drastically decreases the likelihood that you will be able to stick to your diet and eat a calorie-appropriate diet long term. Poor sleep is also associated with poorer mood regulation and thus your dietary adherence may also be reduced by virtue of simply feeling worse and turning to food for comfort.
But even if you were able to stick to your calories despite your poor sleep, you will likely be getting less bang for your buck from the diet. You see, a lot of the hormones that are disrupted when sleep is in a bad place, are the hormones that play a role in how the food you eat is used. Carbohydrate metabolism is negatively affected when sleep is bad,
pushing you towards a more insulin-resistant state. This isn’t great from a health perspective or a muscle-gain/fat-loss perspective either. Fat metabolism is also disrupted when sleep is poor, which leads to faster storage of fat for later use (a calorie surplus is still required to add to your fat stores over time). But with reduced calorie expenditure and potentially increased food intake due to poor sleep, fat gain is more likely. The fat that is stored in this situation also tends to be
visceral fat (the fat stored around your organs), which is the worst type of fat for health. Finally, protein metabolism is also affected by poor sleep. Protein synthesis is reduced (so fewer protein structures (e.g. muscle) are built) and protein degradation is increased (more protein is broken down).
Ultimately, poor sleep leads to reduced muscle anabolism (muscle building), increased fat anabolism (fat storage), increased muscle catabolism (muscle breakdown) and decreased fat catabolism (fat breakdown). While this is a bit of a simplification, and there is obviously a difference between missing an hour of sleep and chronically undersleeping, the general effect is an unfavourable one for those of us who care about our
health, performance and body composition.
Getting good quality sleep brings all of these parameters back into a more advantageous position. However, getting more sleep than is needed, (unfortunately) doesn’t confer massive improvements in
these various parameters. There is a Goldilocks zone with sleep and getting more sleep than you need isn’t likely to improve your health, and may just be detrimental to your overall well-being (sleeping for 10+ hours each day does actually eat into your ability to do other things with your life).
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Paddy Farrell
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