My mom always stressed the importance of sleep. She said not only will I feel grumpy and irritable the next day, but it could effect my school work, my motivation, my mood, and even my weight. When I was younger I didn’t really care much about the weight part, but as I hit my teenage years and got more into health and fitness, it became a big motivation to get proper amounts of sleep. I always believed that it was true because, well, my mom told me it was! But now I am curious to know if lack of sleep and weight gain have any kind of correlation, and if they do, what is it??
Studies have been conducted and have concluded that there is a relationship between sleep loss and weight gain. But no one knew whether or not the relationship was independent or a dependent. In other words, researchers wanted to determine whether lack of sleep has a direct or indirect relationship with weight gain.
This flow chart from “Short Sleep Duration and Weight Gain: A Systematic Review” displays the effects of sleep deprivation and how it can ultimately lead to weight gain and obesity.
Eve Van Cauter is the director of the Sleep, Metabolism, and Health Center at the University of Chicago. She states that a lack of sleep does promote weight gain because it effects certain hormones in the body that influence how much one eats. Someone who is deprived of sleep will have an increased level of ghrelin. This is a hormone produced by the cells in the stomach; this hormone promotes appetite and hunger. Sleep deprivation decreases levels of leptin. This is a hormone produced by the fat cells. It’s purpose is to tell the brain that you are full and have had enough to eat. With an increase in ghrelin and a decrease in leptin, one is likely to eat more than he needs, therefore gaining weight. Being up at late hours of the night where food is readily accessible, and awfully tempting, one has more time to grab a snack or even an extra meal. A study done by Cauter showed that people who lack sleep often eat 300 or more additional calories than they would have if they slept. This is so true for me. If I am up at midnight trying to study or finishing a homework assignment, I always find myself to be snacking on something: a granola bar, pretzels, cookies, anything that is around. These are probably some of the worst things to eat close to bed time anyways because they are so high in sugar which keeps me awake. As shown on the flow chart, the disruption of hormones and the increases time to eat both contribute to an increase in caloric intake.Lack of sleep also causes a disruption of the Endocannabinoid receptors which work with the hormones to regulate appetite, food intake, and energy balance. On the more obvious side, deprivation of sleep causes an overwhelming feeling of fatigue and lack of energy and motivation. Because of this, one is highly unlikely to participate in any physical activity. I know when I am tired all I want to do is sit around and just hangout. I will find every excuse not to go to the gym or do any type of physical activity for that matter. This lack of exercise is a huge contribute to weight gain.
The theory that correlation does not equal causation is true in this case. Reverse causation is a possibility. I have found out that sleep loss can contribute to weight gain, but weight gain can also cause sleep loss. This is because if one lacks physical activity and eats poorly, there is more of a chance that he/she will have trouble sleeping due to discomfort or a rush of energy due to the sugar and/or caffeine in the junk food. People who are active and exercise on a regular basis tend to get better sleep. In addition to exercising, if they sleep more it allows for less time to eat, therefore not allowing for weight gain.
A set of studies were completed by Kristen Knutson, a member of the Department of Health Studies at the University of Chicago, determined the relationship between sleep and weight gain among different age groups. Each study showed similar results which allowed for the conclusion that sleep deprivation can influence weight gain. Those most at risk of weight gain due, in part, to lack of sleep are children and teens. The study results composed of 8,274 children between the ages of six and seven. The results showed that kids who go 9-10 hours of sleep had an odds ratio for obesity of 1.49, 8-9 hours of sleep : 1.89, and less than 8 hours : 2.89. This study also showed that for teens, boys are more susceptible to sleep deprived weight gain than girls. This study was composed of 4,486 teens between 11 and 16. One of the most outstanding results was that for those who got 8 hours or less of sleep, the odds ratios were very different for boys (5.5) than they were for girls (2.1). Knutson stated that with each hour of lost sleep, the risk of obesity increased by 10% in boys, but not so significant in girls. The next study comprised of 3,158 adults. The odds ratios for obesity were less than 5 hours of sleep : 1.85, 6-7 hours : 1.24, and 7-8 hours : 1.09. All of these studies resulted in an increased odds ratio for obesity in relation to less hours of sleep.
Although sleep is key to a normal functioning brain and body, it is also important to know how much sleep you should actually be getting. Eight to ten hours of sleep is an average amount for teens. Most teens struggle to get this much sleep, I know I am one of them. But some teens sleep more than they do anything else. This can also contribute to weight gain because it causes for a lack of physical activity. The bar graph from “The Association Between Sleep Duration and Weight Gain” shows the relationship between different-length sleepers, and weight gain.
Bottom line is sleep deprivation effects many hormones and regular functions of the human body. If a regular-eater experiences a lack of sleep, then he/she will most likely eat more food than needed, therefore gaining weight. Lack of sleep can cause weight gain with additional variables, so lack of sleep does not directly cause weight gain, but it does have an effect on it.
Links to my sources:
http://onlinelibrary.wiley.com (Google Scholar)
http://www.ncbi.nlm.nih.gov/pmc (Google Scholar) – Source of Weight Gain v. Sleep bar graph
http://onlinelibrary.wiley.com (Google Scholar) – Source of Sleep Loss web
http://ebm.sagepub.com/content/230/4/225.short (Google Scholar)