Most people think they gain weight when they lose sleep simply because they have more hours in the day to eat. This makes sense. I remember many nights on call as a Resident at St. Louis Children’s Hospital eating large amounts of high-calorie, unhealthy food as quickly as I could. I got into this eating pattern because I didn’t know if I would be able to eat again all night. As it turns out, this sort of eating pattern is not the full explanation for the relationship between less sleep and more weight. There are decades of research on this subject that have shown that good sleep, both in quality and duration, is essential to help control weight and also to prevent type II (adult-onset) diabetes.
Epidemiological (population) research has shown an association between reduced sleep and increased rates of obesity and type II diabetes. The numbers are surprising. For example, a study has shown that children with reduced sleep were 89% more likely to be obese. Adults with reduced sleep were 55% more likely to be obese. Furthermore, there is a dose relationship. The shorter the sleep, the greater the risk of obesity. With regard to type II diabetes, reduced sleep increased the risk of developing this disease by 28%. For people who have difficulty remaining asleep (fitful sleepers), the risk of developing type II diabetes is increased by 84%. Interestingly, people who had “long sleep” of more than 8-9 hours a night had a 48% increased risk of developing type II diabetes. To be clear, epidemiological associations do not prove that stimulus X causes effect Y (e.g. decreased sleep causes obesity or diabetes), but that stimulus X is associated with effect Y. In the case of sleep and obesity or diabetes, the association appears to be very strong.
The main mechanism that appears to link reduced sleep with obesity is the actions of the two hormones, leptin and ghrelin. These hormones help regulate the feeling of hunger. Leptin makes people feel full, while ghrelin makes people feel hungry. Lack of sleep leads to less production in the body of leptin and more production of ghrelin. Consequently, lack of sleep makes people both feel less full and more hungry. To put this concept into real-life terms, a meal that would “fill-up” someone getting 7-9 hours of sleep a night (the national recommendations), wouldn’t feel like enough for someone who only gets 5 or 6 hours of sleep a night.
There are other mechanisms whereby reduced sleep can lead to obesity. Sleep restriction is associated with stimulation of brain regions sensitive to food stimuli. This suggests that sleep loss may lead to obesity through the selection of high-calorie food (sleep-deprived people are more likely to grab a bag of chips than a bag of carrots, for example). In addition, there is evidence that restricted sleep can lead to the activation of genes that promote obesity. Supporting this concept is the observation that the inheritability of increased body mass index is increased in people who get little sleep.
Sleep loss also affects how people process glucose (sugar). Studies have shown that sleep loss leads to decreased sensitivity, of the body, to the hormone, insulin. This hormone is responsible for helping the body to process glucose and get it out of the blood stream. If the body detects that there is too much glucose in the blood stream, such as what would happen if there is decreased sensitivity to the effects of insulin, then cells in the pancreas, called beta-cells, respond by making more insulin. However, in sleep-deprived people the beta-cells do not make enough extra insulin to overcome the decreased sensitivity of the body to insulin. Therefore, sleep-deprived people have decreased glucose tolerance (they cannot get rid of extra glucose in the blood stream as well as they need to) and this leads to increased risk of developing diabetes.
Another reason why sleep-deprived people have decreased glucose tolerance is brain metabolism. The human brain consumes up to two third of circulating glucose. However, after sleep deprivation, utilization of glucose by the brain is reduced. Therefore, sleep deprivation leads to another mechanism whereby blood glucose cannot be processed correctly, increasing the risk for developing diabetes.
Obesity and type II diabetes are metabolic diseases that have a tremendous impact on public health and society. The role of poor sleep, either in terms of quantity or quantity, or both, is not commonly considered in the management of these conditions. In clinical practice, it is, therefore, important to consider improving sleep as a therapeutic tool in the management of these obesity and type II diabetes.
For those people who are starting fitness programs, those people who are struggling to reach or maintain a goal healthy weight, or experienced athletes who desire to maintain an ideal body composition, it is important to think about good sleep. Aside from the main targets of weight control: diet and exercise, good sleep, which is defined as 7-9 hours a night for adults age 18-64, is essential.
Please see my article, “Top 12 Tips To Improve Sleep,” to help you get started.
Published April 4, 2015
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Morselli L, Leproult R, Balbo M, et al. Role of sleep duration in the regulation of glucose metabolism and appetite. Best Pract Res Clin Endocrinol Metab. 2010 Oct;24(5):687-702.