It has long been known that sleep deprivation is harmful for our health, but new research suggests that losing just half an hour of sleep can have long-term consequences for body weight and metabolism.
“While previous studies have shown that short sleep duration is associated with obesity and diabetes, we found that as little as 30 minutes a day sleep debt can have significant effects on obesity and insulin resistance at follow-up,” said lead study author Dr. Shahrad Taheri.
For the study, Dr. Taheri and his colleagues from Weill Cornell Medical College in Doha, Qatar, recruited 522 patients who had been recently diagnosed with type 2 diabetes. At the start of the study, the participants’ height, weight and waist circumference were measured and samples of their blood were analyzed for insulin sensitivity. The participants were also asked to keep sleep diaries, from which their weekday “sleep debt” was calculated.
At baseline, participants who had weekday sleep debt were found to be 72 percent more likely to be obese, compared with participants who had no weekday sleep debt. By follow-up at 6 months, the association between weekday sleep debt and obesity and insulin resistance was found to be significant.
At the 12-month follow-up, the researchers calculated that every 30 minutes of weekday sleep debt was associated with a 17 percent increase in the risk of obesity and a 39 percent increased risk of insulin resistance.
The team presented their findings at ENDO 2015, the annual meeting of the Endocrine Society in San Diego, CA.
Metabolic effects of sleep deprivation
The new research adds to a growing line of evidence linking sleep to metabolic function and, ultimately, to body weight. In one study, researchers at the University of Chicago Medical Center (UCMC) found that just six nights of limited sleep (four hours a night) can lead to striking changes in glucose tolerance and endocrine function — changes that resemble the effects of advanced age or the early stages of diabetes.
Experts also believe that chronic sleep deprivation may lead to elevated levels of the stress hormone, cortisol. Elevated cortisol may in turn promote insulin resistance, in which the body can’t use the hormone insulin properly to help move glucose into cells for energy. In the UCMC study, the researchers found that the ability of the body to secrete insulin fell by a drastic thirty percent in the typical sleep deprived individual. It also took forty percent longer for a sleep deprived person’s body to control their blood glucose levels following an injection of glucose.
Heightened cortisol also prompts the body to store more fat and be more inclined to use other soft tissue, such as muscle, as energy, which means that sleep-deprived dieters lose more muscle and gain more fat than do those who are well rested. One study found that after two weeks of minor calorie restriction (10 percent less than their daily energy expenditure), subjects who were getting 5.5 hours in bed a night lost just 0.6 kilogram of fat but 2.4 kilograms of other tissue, such as muscle; subjects who got 8.5 hours slumber each night lost 1.4 kilograms of fat and 1.5 kilograms of other tissue.
Further, research shows that sleep loss reduces levels of the hormone leptin, an appetite suppressant, while boosting levels of ghrelin, an appetite stimulant. That’s a poor combination that may prompt sleep-deprived people to eat more. To make matters worse, sleep deprivation also increases cravings for carbohydrates and sweets.
Overall, people who get less than six hours of sleep a night are twice as likely to develop diabetes in their lifetime as those who get seven hours of sleep, and the link between sleep deprivation and obesity is even stronger.
Making time for sleep
New guidelines from the National Sleep Foundation call for most adults to get at least 7-9 hours of sleep per night, but most Americans fall short of that target. Cutting back on sleep is an extremely common response to the time pressures of modern societies. The average night’s sleep decreased from about nine hours in 1910 to about seven hours and 30 minutes in 1975, a trend that continues to this day.
Often, people accumulate sleep debt during weekdays and then try to make up for the lost sleep over the weekend. However, Dr. Taheri says the new findings indicate that even minimal sleep loss is additive and has metabolic consequences:
“Sleep loss is widespread in modern society, but only in the last decade have we realized its metabolic consequences,” he said. “Our findings suggest that avoiding sleep debt could have positive benefits for waistlines and metabolism and that incorporating sleep into lifestyle interventions for weight loss and diabetes might improve their success.”
Practicing good sleep hygiene can help to improve the quality of your sleep and reduce the severity of sleep conditions like insomnia. The National Sleep Foundation recommends the following:
- Establishing consistent sleep/wake schedules
- Creating a regular, relaxing bedtime routine
- Establishing a dark, quiet and comfortable sleep environment
- Sleeping on a comfortable mattress and pillows
- Using the bedroom only for sleep and sex, not for watching TV or using a computer
- Exercising regularly
- Avoiding caffeine/alcohol close to bedtime.