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01/07/2005 - Articles

Sleep Well and Get Thin?

By: Robert W. Griffith, MD


Sleep Well and Get Thin?

Summarized by Robert W. Griffith, MD
January 7, 2005


Most overweight people eat too much, because they have large appetites. In recent years two hormones have been identified that help to regulate appetite - leptin and ghrelin. Leptin decreases appetite, whereas ghrelin increases it. When leptin levels are high, people eat less, but they eat more when ghrelin levels are raised.

It's well known, from studies in rats and humans, that sleep deprivation is associated with an increase in appetite. It may be pertinent that during the past 40 years, the average duration of sleep reported by people in the United States has decreased by almost 2 hours, whereas the incidence of obesity has nearly doubled. Perhaps lack of sleep changes the appetite hormone levels? A small study done in Chicago has looked into this. The findings are reported in the Annals of Internal Medicine, and are summarized here.

What was done

12 healthy young men volunteered for the study. Their average age was 22, they had a normal body mass index (BMI), they didn't smoke, and they weren't taking any medications. They were randomly allocated to either two days of sleep restriction (4 hours of sleep a night) and two days of sleep "extension" (as much sleep as they wanted), or the same procedures but in reverse order.

Plasma leptin and ghrelin levels were measured at intervals during each day and questionnaires were used to rate hunger and appetite. Total calorie intake and the amount of exercise done were kept constant over the four days of the study.

What was found

Sleep was limited to 4 hours each night during the period of sleep restriction; on the days of sleep extension, the subjects averaged 10 hours of sleep.

During the days following sleep restriction, there was an 18% decrease in the leptin levels, a 28% increase in the ghrelin levels, a 24% increase in hunger, and a 23% increase in appetite (especially for high-carbohydrate foods), compared with the findings on the days of extended sleep.

What this means

In summarizing their findings, the investigators state that short duration of sleep in young, healthy men is associated with decreased leptin levels, increased ghrelin levels, and increased hunger and appetite. They call for further studies to see whether chronic lack of sleep may be a risk factor for obesity.

An accompanying editorial in the same journal1 also suggests that controlled studies must be done to measure the effect of sleep-promoting measures on appetite and body weight. The writer points out that this small study does not prove any cause-and-effect relationship between the two hormones measured and the hunger reported; other factors, such as cortisol, can affect sleep and body weight. Nevertheless, the results are intriguing. Those people battling obesity should exercise during the day (to help combat insomnia), and get a good night's sleep - this can do no harm, and may help reduce their food intake.


  • Brief communication: Sleep curtailment in healthy young men is associated with decreased leptin levels, elevated ghrelin levels, and increased hunger and appetite. K. Spiegel, E. Tasali, P. Penev, E. Van Cauter, Ann Intern Med, 2004, vol. 141, pp. 846--850

1. A good night's sleep: Future antidote to the obesity epidemic? JS. Flier, JE. Elmquist, Ann Intern Med, 2004, vol. 141, pp. 885--886

Related Links
Sleeping Your Way to Longevity
Are You Sleeping Too Long?

Created on: 01/04/2005
Reviewed on: 01/07/2005

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