If you got out bed feeling irritable and worn out, you have plenty of company. Evidence suggests that up to 60% of us have problems sleeping and only a lucky minority manage the recommended seven hours a night. Of course we all know that lack of sleep leads to poor concentration, mood change and depression, but recent studies suggest that the waistline as well as the brain may be adversely affected.
Researchers in Sweden, Germany and the USA have found a consistent association between poor sleep patterns and weight gain. In one study, those who slept just 5 hours a night were 50% more likely to be obese than those who slept for 8-hours, whilst those who slept for around 6 hours, were 23% more likely to be obese.
There are several possible explanations for this. Sleep-deprived people may be too tired to exercise, decreasing the calories “burned" through physical activity. In fact studies show that even after just one night of disrupted sleep, study participants tended to move around a lot less and so burned fewer calories. It might also be that people who don’t get enough sleep take in more calories simply because they are awake longer and have more opportunities to eat. Research from Columbia University has shown that when people are sleep deprived, they eat almost 300 calories a day more than when they are well rested. Interestingly, women tended to eat rather more than the men (329 calories vs 263). Most of the extra calories came from fattening foods such as ice-cream, cakes and chocolate.
The mechanism underlying these findings is that sleep deprivation alters the balance of two hormones which are intimately involved in appetite regulation and which have precisely opposite effects. Ghrelin is an appetite stimulant which promotes hunger (and eating), whereas leptin promotes a feeling of satiety (fullness). Think of ghrelin as the driver of appetite and of leptin as the brake. It turns out that sleep deprivation is consistently associated with an increase in ghrelin and a decrease in blood leptin. In one study, people who routinely slept five hours a night had a 14.9% higher level of ghrelin and a 15.5% lower level of leptin than those who slept eight hours. So not getting enough sleep can have a double whammy: an increase in appetite and a reduction in levels of physical activity; the perfect recipe for weight gain.
But would sleeping longer lead to weight loss? Could you literally “sleep it off”? The simple answer is that we don’t know yet, thought studies are underway. Still, experience suggests that asking people to have an extra hour in bed is likely to be a more popular message than telling them to eat less and exercise more!
Dr David Ashton MD PhD
12th December 2012