Can you diet while you’re sleeping?
If someone told you that staying in bed for an extra hour a day was a great way to lose weight, you’d probably think you were dreaming - but UK’s health experts are just waking up to this reality.
In May officials at UK’s Department of Health heard new evidence that being overweight is linked to lack of sleep. Forty years ago, people slept for an average of eight or nine hours, but this has now dropped to just seven. At the same time, incidence of obesity has almost doubled. These figures might seem unrelated at first, but take a close look at the facts.
When we don’t get enough sleep, our bodies become sleep-deprived. This makes us voraciously hungry. Also, during times of food starvation we sleep less. It’s all because the hormones that sharpen our appetite and regulate our metabolism are modified by sleep.
Studies have shown that those who get the least sleep have the highest body mass index. Researchers also found that in children, short duration of sleep at the age of three was one of the main contributors to childhood obesity.
You might think it’s logical that if you sleep more you’re doing less exercise and your weight is bound to rise. In fact the opposite seems to be true. When we are sleep-deprived, the hormones that boost our appetite kick in and encourage us to eat more. At the same time the hormones that tell us we’re full are reduced. The result is, we have to eat more to satisfy these needs.
Dr Shahrad Taheri of the University of Bristol is one of the few scientists in Britain studying these phenomena. His research was presented last month to the UK’s Department of Health officials who visited his obesity clinic in Bristol.
He showed that the body has a fine tuned sense of sleep and wakefulness. Our natural programming means if you’re awake it must be daytime and time to eat, whereas sleep means it’s night and you don’t need much energy, so there’s no need for food.
If we forcibly change our natural rhythms - that’s when the problems start. By staying awake you’re convincing your body that it needs more fuel. Whether you’re up dancing the night away, or sitting in front of the TV, the effect is just the same.
It’s your hormones that cause this change, and the key player is cortisol – the stress hormone, which rises and falls naturally during the day, peaking at around 10am to noon. Sleep deprivation plays havoc with this natural pattern. When fit young men were given only four hours sleep for just six days, the fall in their cortisol levels was six times slower than normal – meaning levels were still high by the evening. Scientists already know that high levels of cortisol means obesity.
On top of high levels of cortisol, Dr Taheri’s studies found that the levels of two other important hormones were thrown out of balance. Ghrelin, a stomach hormone that induces appetite was also raised by 15 per cent. At the same time leptin was lowered by 15 per cent. A lack of leptin convinces you that you’re starving – yet another reason for a visit to the fridge!
So what can you do if you want to lose weight, but find that you’re hungry? First get enough sleep. A sleep deficit makes your body think you’re being deprived of a massive 900 calories a day, and it’s very hard to resist that level of hunger. If you’re already on a diet, the effect will be worse, as your body will react with soaring levels of ghrelin, making you extra hungry. Once your sleep patterns are regulated that feeling of hunger will soon disappear.
So if you find yourself watching TV until after midnight, don’t be surprised if you get an attack of the munchies. It’s your wake-up call to go to bed!
Other Sleepy Facts
- Sleep improves your IQ
- It reduces your risk of substance abuse and even suicide
- Sleep encourages creativity
- It may make you live longer
- You’ll be better at problem solving
- Some studies indicate changing hormone levels during sleep may offer protection against cancer
- Facts memorised at night are remembered better after a good night’s sleep