Many research studies have demonstrated that not getting enough sleep affects the body’s ability to manage blood sugar levels and appetite, increasing the risk of obesity and diabetes.
Human sleep is generally consolidated to a single seven to nine hour period, leading to an extended period of fasting overnight. Both pancreatic cell responsiveness and insulin sensitivity are influenced by sleep. There is reduced glucose tolerance (ability of the body to respond to and use up glucose) during early evening sleep, attributed to several mechanisms such as a reduction in the insulin secretory response, a decrease in the brain uptake of glucose because of slow wave sleep, and a reduction in the body’s general use of glucose.
During the latter part of the night, glucose tolerance begins to improve, and glucose levels progressively decrease toward morning values. This is reflective of increased glucose uptake partly because of decreased slow-wave sleep and increased rapid eye movement sleep. These modulatory effects of sleep on glucose regulation can also be observed when the sleep period happens during daytime.
The duration of sleep is dictated by individual and societal needs. Lack of sleep is highly prevalent and has become a hallmark of a modern society. Many investigators have tried to establish the evidence linking lack of sleep and disrupted glucose metabolism.
One of several studies looked at healthy men and found that when compared with extended sleep, two days of sleep curtailment led to higher glucose levels, lower insulin levels, and a 30 percent increase in appetite for high caloric density carbohydrates. The anorexigenic (appetite-reducing) hormone leptin decreased by 18 percent, and levels of the orexigenic factor ghrelin (stomach derived hormone that stimulates appetite) increased by 28 percent.
Taken together, all the research studies suggest that sleep loss and sleep disturbances contribute to the development of insulin resistance and type 2 diabetes through multiple pathways, including a deleterious effect on glucose balance and increased inflammation, adversely affecting appetite regulation, leading to food intake, weight gain, and ultimately obesity.
Interestingly, the Sleep Heart Health Study showed that sleep duration of either six hours or less, or nine hours or more was associated with increased prevalence of diabetes or glucose intolerance, compared with seven to eight hours of sleep per night.
The Nurses Health Study which included around 70,000 middle-aged women who did not have diabetes at baseline, also showed that both long and short sleepers had significantly increased risk for developing diabetes after 10 years.
In summary, the sleep state has definite modulatory effects on glucose balance. Epidemiologic and experimental studies have shown that sleep loss and sleep disturbances are detrimental to metabolic function and may predispose to obesity, and thus provoke or worsen glucose intolerance, or diabetes.