We all know as adults what it takes to lose weight and as parents how to prevent our children from packing on unhealthy pounds in the first place: diet and exercise are the two pillars of any weight-reduction/obesity prevention program. But what if there was a third approach we have been largely ignoring, which could contribute substantially to our ability to achieve and maintain a healthy weight? That important and often overlooked factor: sleep.
A large number of studies now support a connection between both sleep amount and timing and an increased risk of obesity in adults, children and teens. When you examine the trajectory of increasing rates of obesity in the United States and the concurrent decline in average sleep duration, the graphs are nearly parallel, strongly suggesting that there is an association between the two.
Both cross-sectional studies (which look at the relationship between sleep and weight/Body Mass Index [BMI] at Time Point A) and prospective studies (which examine the relationship between sleep duration at Time Point A and BMI at a later Time Point B) have demonstrated that short sleep and increased weight are closely related even when controlling for factors we know to contribute to obesity, like family history, television viewing and socioeconomic status.
Who is Most at Risk?
There also seems to be a relative “sweet spot” when it comes to sleep and weight gain; for example, studies of adults (and some of teens) suggest that an average of seven to eight hours of sleep may be “protective” against obesity, with sleep amounts both less and greater than that sweet spot associated with increased risk. The reasons are complicated, but “long sleepers” may be at higher risk for weight gain — as well as other health complications — due to other contributing factors such as depression and sleep apnea (more on that below).
To add more fuel to the fire, there are also established links between short sleep duration independent of obesity and Type 2 diabetes, hypertension and cardiovascular disease, which are clearly exacerbated in overweight and obese individuals. And if that wasn’t enough, the risk of sleep apnea is greatly increased in obese adults, teens and children, and sleep apnea in and of itself is associated with metabolic dysfunction and increased cardiovascular consequences (like stroke). A perfect storm, indeed.
Your Body on Sleep Loss
While the mechanisms responsible for the sleep-weight link appear to be complex, several themes have emerged. First, experimental studies in which healthy volunteers are brought into a sleep lab and have their sleep amounts curtailed have shown that the levels of two hormones critical to weight loss/gain, ghrelin and leptin, are altered under conditions of sleep loss. Hunger signals in the brain are increased and satiety (“I’m full”) signals decline. The upshot is that sleep-deprived individuals perceive themselves to be hungrier; as a consequence, when given the opportunity to eat more and consume higher calorie foods — especially carbs and high fat foods — they are more likely to do so. Other metabolic parameters like insulin and glucose (sugar) metabolism are also altered under conditions of chronic sleep loss.
There are likely to be important behavioral mechanisms at play. First, because we know that chronic sleep loss directly impacts “executive functions” (which include judgement, decision-making and motivation), there is a likelihood that making healthy food choices and sticking with a diet plan may diminish under conditions of insufficient sleep. Furthermore, if you are too tired to exercise as a result of ongoing sleep loss and fatigue, that factor is also likely to contribute to increased weight gain. Finally, it is well established that mood is adversely impacted by lack of sleep, so the inclination to follow through on any challenging weight reduction program is greatly reduced. A regular regimen of good sleep, it turns out, doesn’t just leave you feeling well-rested; it can lead to a lighter, healthier you.