Below, Orfeu Buxton, PhD, an instructor of medicine at Brigham and Women's Hospital in Boston, and Jana Klauer, MD, a research fellow at the New York Obesity Research Center of St. Luke's-Roosevelt Hospital, discuss the complex relationship between sleep and body weight.

How can sleeping too little affect body weight?
JANA KLAUER, MD: When we sleep too little, we produce more cortisol, the stress hormone in the body. Cortisol, in turn, causes the release of insulin and higher insulin levels are associated with increased weight because insulin is a hormone that promotes fat storage.

ORFEU BUXTON: Another factor associated with sleep restriction that might lead to increase in weight is increased hunger. It seems as if the body responds to sleep restriction by craving more fuel. Leptin is a molecule secreted by fat cells and conveys a satiety signal that says, "There's enough fuel on board." With sleep restriction, even when the level of activity and the amount of calories are constant, the body says, "I need more food." This is inappropriate and may lead to overeating and potentially to obesity in the long term.

What other effects does sleep restriction have on the body?
ORFEU BUXTON: From sleep restriction experiments it's clear that, with just a week of sleep loss, sleeping only four hours a night, insulin levels are higher and the ability of blood sugar to be used is dramatically altered. And these changes developed in healthy young adults in just a week of sleep loss. The alterations of blood sugar metabolism are termed "impaired glucose tolerance," and this is one of the early stages on the way towards full-blown diabetes. Habitual sleep restriction could play a very important role in increasing risk for diabetes later in life, especially if maintained over many years and decades, much like a sedentary lifestyle or poor eating habits. It's not something that catches up with you in a week or in two weeks, but it's something that over decades can shorten your life.

How can sleeping too much affect body weight?
ORFEU BUXTON: It's not clear that sleeping too much has anything to do with increasing body weight. There have been some studies that have associated very long sleep duration (like 10 hours or more) on a regular basis, with obesity or weight gain or even increased mortality. It's not clear at all that it was the sleep that did that, or if sleep was a symptom of some unknown health problem.

How does sleep loss affect your food choices?
JANA KLAUER, MD: When the body's rested, you think clearly and you don't have reduced energy and you're more apt, under those circumstances, to make wise nutritional choices and to select something that's healthy for your body. When you're sleep-deprived, you want to go for an empty calorie energy boost and usually those are carbohydrates that are very low in nutrients and very high in calories.

What is the connection between sleep and exercise?
JANA KLAUER, MD: You might be more tired and you won't give your workout the intensity that you normally would or maybe you'll skip your workout. If you're going to be exercising, you need to rest. When someone switches their sleep pattern to one of increased deep sleep, they wake up renewed. They don't put off going to the gym; they get out of bed, put on their gym clothes and go out the door and exercise. And exercise will help you to sleep deeper and really get into that deep slow-wave sleep. It is a cycle, and exercise will help them to sleep better that night, so I think each kind of helps the other.

Could poor sleep be another risk factor for obesity?
JANA KLAUER, MD: Sleep is just as important as nutrition and exercise in a healthy diet plan. It's very important to give yourself adequate sleep. Americans sleep, during the workweek, an average of 6 hours and 54 minutes and, on the weekends, they add about 40 extra minutes per day. So we do go around a little sleep-deprived.

ORFEU BUXTON, MD: Poor sleep or restricted sleep can potentially be seen as a symptom of a stressful or unhealthy lifestyle. Adequate sleep is a sign of a balanced lifestyle along with diet and exercise. It's been an important recognition that sufficient sleep is important for good health.

Source: Healthology.

December 2004 News Article Index