You may have already come across this in the scientific literature (and the media). Lack of sleep may increase your risk of obesity. For example, Bell and Zimmerman (2010) showed that for infants and pre-school aged children, their risk of overweight/obesity was increased by 80% (or increased by 1.8 times) if they slept for less time. In addition, trying to make up lost night time sleep with day napping did not reduce risk
Another more recent study Carter et al (2011) also showed that longer sleep duration at age 3-5 was associated with a reduction in BMI (0.48 for each extra hour of sleep) and a 61% reduction in the risk of being overweight at age 7. Lack of sleep manifested itself via increased fat deposition. An editorial on the same journal by Cappuccio and Miller (2011) provides a nice short summary.
Move onwards towards adolescence. Olds et al (2011) compared Early-bed/Early-rise vs. Late-bed/Late-rise adolescents and found that the latter were 1.47 times more likely to be overweight or obese, 2.16 times more likely to be obese, 1.77 times more likely to have low moderate-to-vigorous physical (they did, on average, 27 min less moderate-to-vigorous physical activity), and were 2.92 times more likely to have high screen time (they watched, on average, an extra 48 min/d more screen time). Interestingly, both groups slept for similar amounts of time. This suggests that the time of the day when we sleep is important (it is not just about total sleep time).
So, how does not sleeping “help” you gain weight? Two possibilities: you either increase energy intake through not sleeping (so more opportunity/time for eating/snacking) and/or reduce energy expenditure (during the day as a whole because of tiredness and compensating mechanisms). A short commentary by Chaput (2010) in the appropriately named Sleep journal offers several explanations on how lack of sleeping contributes to weight gain. Prominently, he suggests that short sleep duration promotes overconsumption of food via a reward-driven eating behaviour (hedonistic – meaning it is associated with an increased use of food as a reward or source of pleasure). Overall, this potentially contributes to overconsumption of food “in the absence of hunger”.
Why does this matter? This matters because early life sleep patterns may carry through from infancy to childhood, adolescence and adulthood and so become yet another established risk factor for overweight and obesity in adulthood (in excess of 50% of obese adolescents become obese adults). Morale of the story: “Sleep is not a waste of time”.
Interestingly, a trial by Cizza et al (2010) started last year in the US, where they are looking at treating obesity by extending sleep duration (via a randomized, prospective, controlled trial). This 4 year trial will be looking at the impact of increasing sleep duration (from less than 6.5 hours to a healthy 7.5 hours) on body weight, endocrine (leptin and ghrelin) and immune (cytokines) parameters, the prevalence of metabolic syndrome, body composition, psychomotor vigilance, mood, and quality of life. Will this be another weapon in the fight against obesity?
Needed an excuse to sleep more? There you go. I’m going to sleep on that.