Why sleep is so important for your metabolic health.

Poor sleep can cause dementia, heart disease, diabetes and make us fat. Our experts delve into why sleep is so important for your metabolic health and why it should be your priority.

Written by

Dr Claire Merrifield MBBS MRCGP PhD

GP, PhD and our medical director


Key Takeaways

  • People who don’t sleep enough are more likely to be metabolically unhealthy.
  • Poor sleep contributes to overweight and obesity.
  • Just a few days of restricted sleep affects glucose metabolism.
  • Your blood pressure is affected by the amount you sleep.

the saying “I’ll sleep when I’m dead” is all too accurate

Being productive, incessantly busy and instantly reactive on all forms of communication seems to be a modern status symbol and something many people equate with success. You might hear people who are seemingly ultra-productive use the phrase “I’ll sleep when I’m dead” or “I’m too busy for sleep”. These people might proudly get up at 4 or 5 after not achieving a full 7-9 hours of sleep and feel like they’re winning at life.

The reality is their external success may not correlate with their internal health. A 9 year study of people's sleeping habits found that people who sleep less than 6 hours a night were nearly twice as likely to die as those who slept for 7-9 hours1. There are a lot of different reasons for this, most of which are related to the negative effects of poor sleep on your metabolic health.

Sleep - the bigger picture - how sleep deprivation can lead to obesity

Even if you’re not worried about whether you might die of a stroke or heart attack in 20 or 30 years, how your body looks and feels right now probably is important to you. You know how terrible you feel after a poor night's sleep. You might get grouchy, more emotional, have trouble thinking clearly and have less motivation for things like exercise or socialising.

All of us have a bad night's sleep once in a while and our bodies can handle the occasional bit of disruption. But even a few days of sleep restriction can cause people to put on 1 kg in weight. Many other studies have shown a link between people sleeping less than 6 hours a night and obesity. When you put on weight due to poor sleep, it’s often belly fat or visceral fat, which we know is unhealthy and makes it harder to lose weight in the long run. What’s more, this effect happens to people at any age, even children and teenagers2.

How does poor sleep cause obesity?

When you’re sleep deprived:

  • You tend to feel hungrier and eat more
  • You’re drawn to high-fat / high-carbohydrate foods to satisfy your hunger
  • You tend to move less
  • The hormones involved in how hungry and how full you feel are out of balance
  • Your cortisol levels rise which stop you burning fat and promotes weight gain

If you don’t sleep enough you’re more likely to develop type 2 diabetes

Just 4 days of sleeping 4.5 hours a night can cause cells in the body to become insulin resistant, which is a stage on the path to type 2 diabetes3.

How does poor sleep cause type 2 diabetes?

    When you’re sleep deprived:

  • Cortisol levels are higher, this affects how your body handles glucose
  • The body creates more glucose and handles the glucose in your bloodstream less efficiently
  • You have a higher levels of inflammation which contributes to type 2 diabetes
  • Free fatty acid levels are higher, which stops glucose being transferred into muscles, keeping blood sugar high

If you don’t sleep enough your blood pressure is likely to be high

High blood pressure is an important player in your metabolic health. When pressure in your blood vessels is high, it causes the inside of the arteries to ‘roughen up’. This rough surface makes it easier for circulating cholesterol to get stuck in the artery wall, leading to blockages.

Sleeping less than 5 hours a night means you’re twice as likely to have high blood pressure.

These blockages or ‘plaques’ are what ultimately cause heart attacks and strokes. Keeping your blood pressure low is important to reduce your risk of cardiovascular disease and dementia. Sleeping less than 5 hours a night means you’re twice as likely to have high blood pressure. Reducing sleep duration in healthy young adults by 1.5 hours per night for just 8 days led to a rise in blood pressure.

How does poor sleep cause high blood pressure?

When you’re sleep deprived:

  • You tend to eat more and put on weight and weight gain causes high blood pressure
  • Levels of inflammatory mediators increase which increases blood pressure
  • The sympathetic nervous system is stimulated which increases blood pressure
  • The good news is that even increasing the length of time you sleep by 15-30 minutes could have significant benefits on blood pressure4.

    How you sleep tonight affects your health tomorrow

    Woman enjoying the sun

    Getting less than the recommended amount of sleep has major consequences for your health. Those consequences are measurable after just a few days. In the longer term, if you don’t prioritise your sleep you’re at greater risk of having a heart attack, stroke or developing dementia.

    It’s easy to put off sleep in favour of something else: work, fun, family. But ask yourself what’s really important to you? If your health is important and you want to be fit and healthy enough to enjoy the fruits of your labour and your family life in the future, start thinking today about how you can improve your sleep.

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