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If your efforts to lose weight aren't succeeding, your diet may not be the problem. The culprit could be your sleeping habits.

Mounting evidence indicates that sleep deprivation increases the risk of obesity. A new study published online by The American Journal of Clinical Nutrition suggests that even a single night of poor sleep can wreak havoc on weight control by slowing metabolism and increasing hunger.

In the study, researchers compared the effect of regular sleep (eight hours) with one night of total sleep deprivation on the body's energy expenditure (calorie burning) the next morning in healthy young men.

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Compared with after normal sleep, participants' resting metabolic rate was significantly reduced after sleep deprivation. (Resting metabolic rate is the energy required to keep your body functioning including your lungs breathing and your heart beating while at rest. As much as 75 per cent of your daily calorie burning is attributed to your resting metabolic rate.) As well, after eating breakfast, calories burned to digest food was 20 per cent lower when sleep deprived compared with rested.

Participants reported an increased appetite and had higher blood levels of a hunger hormone called ghrelin the morning after a night without sleep. (Ghrelin is produced by the stomach and stimulates appetite and eating.) Sleep-deprived men had a higher blood sugar (glucose) level after eating breakfast than those who had normal sleep, suggesting the body is less effective at clearing glucose from the bloodstream after sleep loss.

Lack of sleep also caused higher levels of cortisol - a stress hormone - the following day. Higher and prolonged levels of cortisol in the bloodstream has been associated with a number of negative health effects including impaired blood sugar control, high blood pressure, lowered immunity and abdominal obesity.

The researchers speculate that chronic sleep loss can trigger weight gain by upsetting hormones that regulate calorie burning in the body.

It's estimated that one in seven Canadians has difficulty sleeping. Causes of poor sleep (insomnia) include stress, anxiety, depression, restless leg syndrome and sleep apnea.

Sleep apnea occurs when the upper airway gets completely or partly blocked during sleep, reducing the amount of oxygen that gets to the lungs. This causes you to wake up to breath properly. These breathing pauses, or apneas, can last up to 30 seconds and can happen many times throughout the night.

Your diet can also prevent you from getting a good night's rest. Eating the right foods in the evening and knowing what foods to avoid can help you get the seven to eight hours of sleep you need each night. (Children and teenagers need nine to 10 hours.)

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Leslie Beck, a Toronto-based dietitian at the Medcan Clinic, is on CTV's Canada AM every Wednesday. Her website is

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