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Sleep deprivation may alter the body's metabolism and make weight loss more difficult, studies suggest.
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updated 1/9/2004 5:54:17 PM ET 2004-01-09T22:54:17

Do you need to lose weight? Then, turn off the television or computer an hour earlier and go to bed. We’re sleeping too little, experts warn. Too much sitting instead of being active is clearly part of why overweight is now common. But studies suggest that a lack of sleep may make weight loss and weight control more of a challenge by altering our metabolism, as well as our eating and activity patterns.

Some research has directly tested the idea that sleep deprivation leads to weight problems. For instance, in a Japanese study of six-and seven-year olds, children who slept nine to ten hours a night were compared to those who only slept eight to nine hours. The latter group was almost twice as likely to be overweight. Children sleeping less than eight hours a night were almost three times as likely to be overweight.

Changes in hormone levels have been linked to sleep deprivation in several studies. One hormone, cortisol, regulates metabolism of sugar, protein, fat, minerals and water. Physical or emotional stress raises cortisol levels. Lack of sleep may also raise levels at certain times of the day.

Second, higher levels of insulin, a condition known as insulin resistance, have also been linked to a shortage of sleep in several studies. Excess cortisol could be the link. Since insulin not only controls blood sugar, but also promotes fat storage, extra insulin makes weight loss more difficult.

Sleep affects behavior
Further research needs to validate the hormonal changes observed. But even without any hormonal impact, sleep deprivation can promote weight gain by affecting our behavior.

When people low on sleep find their energy dropping throughout the day, many turn to food for a pickup. The short-term rise in blood sugar gives a more energetic feeling, but often the extra calories are not needed by the body and must be stored as body fat. Furthermore, the most appealing foods when we feel low on energy are often sweets or refined carbohydrates with low nutrient density. If sleep deprivation causes insulin resistance, overconsuming these types of carbohydrates may be especially problematic.

Not only is it easy to take in excess calories when sleep deprived. For many people, calorie burning decreases. If your extra waking hours are spent in sedentary activities at a desk or computer or in front of the TV, you're not burning many more calories than when asleep. And when sleep deprived, people are often too tired to exercise. Or if they do manage to exercise, they work out less intensely than usual. For example, a rested person may walk two miles in a half-hour, while someone more fatigued may go much less. The tired person would burn fewer calories, despite walking just as long.

Sleep experts recommend at least eight hours of sleep a night for most adults. Yet Americans average just under seven hours during the workweek, according to the National Sleep Foundation. In fact, a third of adults reportedly sleep no more than six-and-a-half hours nightly.

Shutting off the TV an hour earlier means an hour less munching time. It could also shift your metabolism to make weight control easier. It could even leave you with more energy to exercise. Definitely, these are propositions to sleep on.

Nutrition Notes is provided by the American Institute for Cancer Research in Washington, D.C.

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