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3. The Sleep Link to Diabetes

The key underlying problem in type 2 diabetes is insulin resistance, where the body does not make proper use of this sugar-processing hormone. Guess what? When you’re sleep deprived, your body almost immediately develops conditions that resemble the insulin resistance of diabetes.

“In one study of young, healthy adult males, they decreased their sleep time to about four hours per night for six nights,” says Arand. “At the end of those six nights, every one of those healthy young men was showing impaired glucose tolerance, a precursor to developing diabetes.”

Another study found that people in their late 20s and early 30s who slept less than 6.5 hours per night had the insulin sensitivity of someone more than 60 years old.

4. The Sleep Link to Brain Function and Mental Health

If you’re chronically sleep deprived, you may think you’re still driving safely and performing well at your job, but you’re probably wrong. Studies have found that people who aren’t getting enough sleep drive just as unsafely as someone who’s drunk.

“We also know that people who are sleep deprived have very poor judgment when evaluating their own performance. They think they’re doing well on memory or eye-hand coordination tests, but they’re not,” says Arand. “The memory is also slightly degraded when you’re sleep deprived, and gets worse the more deprivation you have.”

5. The Sleep Link to Obesity

Can not getting enough sleep really make you fat? Several studies over the past decade point to a link between sleep deprivation and obesity -- in both adults and children. In one study, people who slept five hours per night were 73% more likely to become obese than those getting seven to nine nightly hours of sleep. In fact, one study found that lack of sleep was a bigger contributor to childhood obesity than any other factor.

Nobody knows exactly why this might be, but some research has pointed to hormonal imbalances as the culprit. For example, lack of sleep has been linked to lower levels of the hormone leptin, which reduces hunger.

The good news in all this is that you can repair the damage from inadequate sleep fairly quickly. “The system is very quick to respond,” says Arand. “For example, the young men in the diabetes study returned to a normal state of glucose tolerance after just a few nights of regular sleep. Many of these conditions will repair themselves -- unless, of course, you get so chronically sleep deprived that you’ve caused permanent damage to your health.”

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