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You've heard it repeatedly: The keys to health - and weight control - are a healthy diet, regular exercise and a good night's sleep.

If you're among the many Canadians who suffer from sleep apnea - a disorder that increases the risk of high blood pressure, heart attack, stroke and depression - your symptoms could be sabotaging your diet.

According to a study published last month in the Journal of Clinical Sleep Medicine, adults with the most severe symptoms of obstructive sleep apnea ate a diet higher in calories, cholesterol and artery-clogging saturated fat than those with less severe symptoms.

Obstructive sleep apnea - the most common form of sleep apnea - occurs when the upper airway gets completely or partly blocked during sleep, and breathing briefly stops. These breathing pauses, or apneas, can last up to 30 seconds and can happen many times throughout the night. The brain senses the breathing difficulty and rouses you from sleep to reopen your airway.

Symptoms of sleep apnea include excessive daytime sleepiness, loud snoring, memory loss and difficulty staying asleep. It's thought that repeated bouts of sleep deprivation boost blood pressure, which over time increases the risk of heart disease and stroke.

The condition is often treated with a mechanical device called CPAP (continuous positive airway pressure) that blows air down the throat to keep the passageway open during sleep.

It's estimated that one in five Canadian adults have mild sleep apnea and one in 15 have at least moderate sleep apnea. Obstructive sleep apnea also affects as many as 3 per cent of children. Alcohol, smoking, obesity and being overweight are lifestyle factors linked with the condition. As many as 70 per cent of all people with obstructive sleep apnea are classified as obese (they have a body mass index of 30 or greater).

In the latest study, involving 320 adults with the disorder, the increasing severity of symptoms was linked with a higher intake of calories, protein, cholesterol and saturated fat. (Symptom severity was measured by the number of breathing disturbances during sleep.) With the exception of cholesterol, these associations were seen mainly in women.

On average, compared to women with less severe symptoms, those with severe sleep apnea consumed 22 more grams of protein (the amount found in three ounces of meat), 28 more grams of total fat, 88 more milligrams of cholesterol and nine more grams of saturated fat. A higher intake of saturated fat can further boost the risk of heart disease by raising blood cholesterol.

It's well known that the severity of sleep apnea is tied to obesity and that obese individuals are more likely to consume more fat and cholesterol. But this new study revealed that severe sleep apnea symptoms affected a person's food intake regardless of body weight.

Previous studies suggest that sleepiness and fatigue influence dietary intake by altering hormones that regulate appetite, which can lead to overeating and weight gain.

The Quebec Family Study, published earlier this year, followed 276 adults and found that short sleepers (five to six hours a night) were 35 per cent more likely than average sleepers (seven to eight hours a night) to experience an 11-pound weight gain over six years.

Sleep deprivation - even in people without sleep apnea - is thought to increase production of ghrelin, the hormone that tells us we're hungry, and decrease production of leptin, the hormone that tells us we're full.

Upsetting the balance of these hormones may also increase cravings for carbohydrates and fatty foods.

Sleep deprivation can affect your diet in other ways, too. Fatigue causes some people to eat more food in an effort to boost energy levels. Feeling tired also reduces the motivation to exercise and burn off excess calories.

If you have obstructive sleep apnea - and even if you don't - it's important to realize how a chronic lack of sleep can affect your eating habits and your weight. The following tips can help you get the seven to eight hours of sleep you need each night. (Children and teenagers need nine to 10 hours each night.)

Lose excess weight

Fat deposits around the upper airway can obstruct breathing during sleep. Losing 10 per cent of your body weight - 22 pounds for a 220-pound man - can greatly reduce the number of sleep apnea episodes each night.

Avoid late-night meals

Don't eat a heavy meal two hours before bedtime. Research suggests that the more fat you eat at your evening meal, the more likely you are to experience sleep disruptions. If you have heartburn, avoid spicy meals that can trigger symptoms and prevent a good night's sleep.

Limit caffeine

Caffeine blocks the action of adenosine, a brain chemical that induces sleep. If you're having trouble sleeping, aim for no more than 200 milligrams a day, and preferably less. (One eight-ounce cup of coffee has 80 to 175 milligrams of caffeine; the same serving size of tea has 45 milligrams.) Avoid caffeine in the afternoon and evening.

Avoid alcohol

If you have sleep apnea, drinking alcohol can make your throat muscles relax more than normal, increasing the chance that airways get blocked. Alcohol can also impair REM (rapid eye movement) sleep, the portion of sleep thought to be important for memory.

Get moving

Regular exercise helps you fall asleep faster, promotes weight loss and relieves stress. Exercise at least three hours before bedtime. A workout right before bed can make falling asleep more difficult.

Quit smoking

Smokers have a threefold greater risk of sleep apnea than non-smokers. Smoking may increase inflammation and fluid retention in the upper airway, disrupting breathing during sleep.

For more information about obstructive sleep apnea, its diagnosis and treatment, visit the Lung Association of Canada website at Lung.ca.

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