The field of public health has labeled a number of epidemics that are currently affecting the United States, with one of the most relevant of these being obesity. Current obesity rates are troubling, with almost 70% of the adults in the U.S. considered to be overweight or obese. Further, almost 7% of the population is considered to have extreme obesity.
Although not yet recognized by all public health officials, there is also a sleep epidemic in the U.S., and it’s also troubling. Compared to 50 years ago, Americans have been getting almost two hours less of sleep per night. According to the National Sleep Foundation, adults need 7-9 hours of sleep per night, but 40% of our population is not attaining this goal. Short sleep duration has been associated with increased morbidity and mortality, metabolic syndrome, type 2 diabetes, cardiovascular disease, and hypertension.
Many researchers do not think that the rise in obesity and decreased sleep time are coincidental. In fact, sleep and obesity has received a lot of research attention over the years. In psychology, and many other scientific fields, we like to perform what is called a “meta analysis.” This is basically a fancy word for taking all the studies done on a particular topic, and combining the results to see if there are consistent findings.
In 2008, there was a meta analysis done on sleep duration and obesity. This meta analyses was the first of its kind, because it looked at populations all over the world and also all ages. The results showed consistent odds that, if you are a short sleeper, you are also more likely to be obese.
However, directionality could not be drawn from this specific study. There are some suggested mechanisms behind this relationship though. Short sleep may lead to some hormonal responses, which then increase appetite. More specifically, short sleep associated with changes in leptin and ghrelin, which increase appetite. There is also potential for some behavioral snowball effects. Short sleep makes you more fatigued, which decreases your chance of exercising, which can lead to weight gain, which can lead to poor sleep….
While there is plenty of research looking at how short sleep time may cause obesity, there is little examining the other part of the relationship; how can food intake effect sleep? A recent study tackled this question, and recruited 52 men and women to participate. It is important to note that these participants were young adults, non-smokers, healthy, non-obese, and good sleepers.
Participants completed a detail record of their diet, and were then invited to spend a night in the sleep laboratory. They were then hooked up to a polysomnograph (the gold standard for sleep research). Researchers found that food intake, primarily at night, was significantly associated with sleep quality. In particular, food intake was associated longer sleep latency (the time it takes to fall asleep), less REM sleep, and more awakenings throughout the night. These findings were even more pronounced for women.
This is an important area of study. Sleep is very influential on daytime behaviors, such as diet, and vice versa. Sleep has significant implications for overall health, and should be seen as an important factor when considering diet and weight. Future research endeavors will hopefully shed light on some of the specific mechanisms in the relationships between sleep and obesity.
Cappuccio, F. P., Taggart, F. M., Kandala, N. B., & Currie, A. (2008). Meta-analysis of short sleep duration and obesity in children and adults. Sleep, 31(5), 619.
Crispim, C. A., Zimberg, I. Z., dos Reis, B. G., Diniz, R. M., Tufik, S., & de Mello, M. T. (2011). Relationship between food intake and sleep pattern in healthy individuals. Journal of clinical sleep medicine: JCSM: official publication of the American Academy of Sleep Medicine, 7(6), 659.