I like my sleep and think I need at least 8 hours if I’m not to be too grumpy the next day. I was therefore interested to see this headline on the BBC this week: ‘Why reducing sleep makes you hungry’. I certainly remember that when working as a junior doctor with lots of on call and not much sleep, a busy night would mean that I was more likely to seek out biscuits, chocolate and cake the next day. Nowadays, I don’t do on call, but I find getting up early to travel to a meeting has the same effect.
So, is there any evidence that this is true, or do I just using being tired as an excuse to indulge? Luckily, there have been a few studies published recently. A useful review of the evidence was published in the European Journal of Clinical Nutrition this year by academics at King’s College, London (for more information click here). The results suggest that sleep deprivation may result in increased energy intake with no difference in energy expenditure, leading to an extra 385 calories eaten that aren’t burnt off per day (I guess that’s about a chocolate bar). Although you might therefore expect that reduced sleep might result in obesity, the researchers commented that they were unable to analyse whether food choice was altered, or whether there is an effect on long-term weight gain, as good evidence is surprisingly scarce.
Is this also a problem in children? I couldn’t find much about sleep duration and hunger or appetite in children but a number of studies, mainly in older children suggest that those who sleep less than their peers have an approximate doubling of the risk of overweight and obesity. These studies don’t tell us whether sleep deprivation actually causes obesity, or how it might lead to obesity, and they don’t tell us what other lifestyle factors might be important in determining both the amount of sleep children get and their risk of obesity. Researchers working in the brilliant Born in Bradford study published a paper in the journal Sleep this year (which you can find here) in which they studied more than 1000 children between 12 and 36 months of age. The study showed that less sleep was associated with increased fat in South Asian children and interestingly, also suggested that obesity may be a consequence of decreased sleep even in young children.
Despite the lack of clarity in the literature I will continue to insist that getting up early in the morning is NOT good for me, particularly at the weekends. Given our busy lives and the prevalence of televisions, computers, mobile phones in bedrooms which can, and do disrupt our (and our children’s) nights we should remember the importance of sleep!