A growing body of research suggests that there’s a link between how much people sleep and how much they weigh. If you’re not sleeping enough, the effects could be more significant than just dark circles under your eyes. Here we look at the surprising fact of how your size and your sleep are closely linked.
The rise of obesity over the last few decades is paralleled by significant reductions in the length of time we spend asleep.
At the same time, a large number of studies have reported associations between impaired sleep and the likelihood of developing obesity or diseases such as type 2 diabetes. (Note: the act of sleeping less does not in itself make you fat – after a few disturbed nights your body won’t automatically have created fat!).
We’re not talking about a cause/effect link here. We’re talking correlation. As the number of people getting less sleep has risen, so the number of people at risk of life-threatening metabolic and cardiovascular diseases has risen too. The reason for this correlation may lie in the effects that poor or less sleep may have on your behaviour and physiology. It’s these effects that can contribute to weight gain.
Inactivity – if you’re feeling lethargic and tired, you’re less likely to exercise and more likely to take shortcuts like using the lift rather than the stairs. This decreases the amount of calories you’re burning, which has a direct effect on your weight.
Mood fluctuations – sleep is vital to regulating your mood. Less sleep could see you happy one moment and feeling low the next. Low mood can trigger emotional or ‘comfort’ eating, when our bodies crave high fat, high sugar foods. When eaten, these foods trigger the pleasure response in your brain, and we’re hardwired to crave them in times of distress.
Reduced leptin levels – less of the hormone that tells you you’re full could see you overeating without realising it.
Increased grehlin levels – more of the hormone that tells you you’re hungry will have you seeking out more food and snacks, even if you’ve consumed the right amount of food for you that day.
Recent analysis conducted by King’s College London reviewed dozens of small studies involving sleep and appetite. It showed that, although not everyone is affected in the same way, on average getting less than seven hours of sleep a night led to people eating significantly more overall.
A bad night’s sleep disrupts the two key hunger hormones, ghrelin and leptin and this combination leaves us feeling physically hungrier, causing us to eat more. Studies also suggest that when we’re exposed to food while sleep deprived, there is increased activation in areas of the brain associated with reward. This can lead to us choosing foods that are higher in sugar and fat, rather than selecting healthy options.
All of this can help to explain why, in the long term, there’s a strong connection between poor sleep, weight gain and health problems like type 2 diabetes. The simple solution is to make sure you’re getting enough sleep. For adults, 7-8 hours of sleep per night is associated with the lowest risk of incidence of cardiovascular diseases.
Find out more:
- The big sleep experiment – Trust me I’m a Doctor
- The effects of insufficient sleep and circadian rhythm disruption – PNAS
- The Surrey Sleep Research Centre – Dr Derk Jan-Dijk (University of Surrey)