“Gremlin? No, ghrelin.” By Victoria S. Brkovich, MD

This month the American Heart Association meeting in San Diego presented a study that further supports the idea that lack of sleep contributes to obesity.

Researchers at Mayo Clinic in Rochester, MN, tested whether lack of sleep altered the levels of the hormones leptin and ghrelin, increased the amount of food people ate, and affected energy burned through activity.  The hormones leptin and ghrelin are associated with appetite.  Ghrelin, which is produced in the gastrointestinal tract, stimulates appetite, while leptin, produced in fat cells, sends a signal to the brain when you are full.

The researchers studied 17 normal, healthy young men and women for eight nights, with half of the participants sleeping normally and half sleeping only two-thirds their normal time.

Participants ate as much as they wanted during the study.

Researchers found:

  • The sleep deprived group, who slept on average one hour and 20 minutes less than the control group each day, consumed about 550 more calories per day.
  • The amount of energy used for activity didn’t significantly change between groups, suggesting that those who slept less didn’t burn more calories.
  • Unexpectedly, the lack of sleep cohort was associated with increased leptin levels and decreasing ghrelin — changes that were more likely a consequence, rather than a cause, of over-eating.

Leptin and ghrelin are two hormones that have been recognized to have a major influence on energy balance.  Leptin is a long-term regulator of energy balance, suppressing food intake and thereby inducing weight loss.  Ghrelin on the other hand is a fast-acting hormone, playing a role in meal initiation.

In light of this study, what if you feel that you go to bed early to get a good night’s rest, but still feel fatigued and are having difficulty with weight maintenance?  Obstructive sleep apnea, which snoring is a common sign, may be the issue.  The disruptions suffered in sleep apnea effectively reduce the amount of restorative sleep.

Patients who suffer from sleep apnea are more likely to be obese.  Patients with sleep apnea also have uncharacteristically high levels of leptin.  What’s more, when their apnea is treated, leptin levels drop — and somehow that helps them to lose weight.

So why does low leptin seem to cause weight gain in some folks while allowing others to lose weight?  One theory says that it may not be the level of this hormone that matters so much as a person’s individual response to it.  In much the same way that obese people can become resistant to insulin and develop diabetes, people with apnea may be resistant to the fullness signal that leptin sends to the brain.

It is known that in obese subjects the circulating level of leptin is increased, whereas the level of ghrelin is decreased. It is now established that obese patients are leptin-resistant. However, the manner in which both the leptin and ghrelin systems contribute to the development or maintenance of obesity is still not clear, and continues to be studied.

Until doctors do know more, most experts agree that if you are dieting, making sure you get at least 7 to 8 hours of sleep a night is not a bad idea, particularly if you get six hours of sleep or less a night currently.  You may just discover that you aren’t as hungry, or that you have lessened your craving for sugary, calorie-dense foods that you reach for just to stay energized.  This change alone translates to fewer calories consumed.

And again, on the other hand, if you already sleep a lot, or you increase your sleep and feel even more tired, you should talk to your doctor. Experts say you may be one of the thousands of people with undiagnosed sleep apnea.

Simply put, with continued research, more and more data shows that you simply can’t cut back on sleep without paying some price.

 

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