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But as wild as the idea sounds, substantial medical evidence suggests some
fascinating links between sleep and weight. Researchers say that how much you
sleep and quite possibility the quality of your sleep may silently orchestrate
a symphony of hormonal activity tied to your appetite.
"One of the more interesting ideas that has been smoldering and is now gaining
momentum is the appreciation of the fact that sleep and sleep disruption do
remarkable things to the body -- including possibly influencing our weight,"
says David Rapoport, MD, associate professor and director of the Sleep Medicine
Program at the New York University School of Medicine in New York City.
While doctors have long known that many hormones are affected by sleep, Rapoport
says it wasn't until recently that appetite entered the picture. What brought
it into focus, he says, was research on the hormones leptin and ghrelin. First,
doctors say that both can influence our appetite. And studies show that
production of both may be influenced by how much or how little we sleep.
In fact, have you ever experienced a sleepless night followed by a day when no
matter what you ate you never felt full or satisfied? If so, then you have
experienced the workings of leptin and ghrelin.
How Hormones Affect Your Sleep
Leptin and ghrelin work in a kind of "checks and balances" system to control
feelings of hunger and fullness, explains Michael Breus, PhD, a faculty member
of the Atlanta School of Sleep Medicine and director of The Sleep Disorders
Centers of Southeastern Lung Care in Atlanta. Ghrelin, which is produced in the
gastrointestinal tract, stimulates appetite, while leptin, produced in fat
cells, sends a signal to the brain when you are full.
So what's the connection to sleep? "When you don't get enough sleep, it drives
leptin levels down, which means you don't feel as satisfied after you eat. Lack
of sleep also causes ghrelin levels to rise, which means your appetite is
stimulated, so you want more food," Breus tells WebMD.
The two combined, he says, can set the stage for overeating, which in turn may
lead to weight gain.
Studies: Those Who Sleep Less Often Weigh More
How the hormones leptin and ghrelin set the stage for overeating was recently
explored in two studies conducted at the University of Chicago in Illinois and
at Stanford University in California.
In the Chicago study, doctors measured levels of leptin and ghrelin in 12
healthy men. They also noted their hunger and appetite levels. Soon after, the
men were subjected to two days of sleep deprivation followed by two days of
extended sleep. During this time doctors continued to monitor hormone levels,
appetite, and activity.
The end result: When sleep was restricted, leptin levels went down and ghrelin
levels went up. Not surprisingly, the men's appetite also increased
proportionally. Their desire for high carbohydrate, calorie-dense foods
increased by a whopping 45%.
It was in the Stanford study, however, that the more provocative meaning of the
leptin-ghrelin effect came to light. In this research -- a joint project
between Stanford and the University of Wisconsin -- about 1,000 volunteers
reported the number of hours they slept each night. Doctors then measured their
levels of ghrelin and leptin, as well as charted their weight.
The result: Those who slept less than eight hours a night not only had lower
levels of leptin and higher levels of ghrelin, but they also had a higher level
of body fat. What's more, that level of body fat seemed to correlate with their
sleep patterns. Specifically, those who slept the fewest hours per night
weighed the most.
Eating and Sleep Apnea: The New Connection
As a result of these and other studies, researchers began to theorize that
getting more sleep just might be the answer to society's burgeoning waistline.
But before you trade the cost of your gym membership for a pricey new mattress,
take note: Experts also say the relationship is not as obvious as it seems.
The reason: Enter the somewhat mysterious nocturnal ailment known as
"obstructive sleep apnea." People with sleep apnea may stop breathing for up to
a minute, sometimes hundreds of times during the night while sleeping, says
Dominic Roca, MD, director of the Connecticut Center for Sleep Medicine at
Stamford Hospital.
Though the exact cause of the problem remains unknown, Roca and others believe
that in most instances physical abnormalities inside the mouth and neck cause
the soft tissue in the rear of the throat to collapse. This briefly closes off
air passages many times during a night, causing disruption in breathing and a
tendency to snore.
The end result: Although you may go to bed early and think you are getting a
good night's rest, the disruption in breathing prevents you from getting deep
sleep. Eight hours of disrupted shut eye can leave you feeling like you had
only four.
"You wake up feeling tired and continue to feel tired all day," Roca tells
WebMD.
The Link Between Sleep Apnea and Weight
So what does sleep apnea have to do with weight gain?
First, says Roca, patients who suffer from sleep apnea are more likely to be
obese. However, studies show they do not have the usual low leptin levels
associated with being overweight. In fact, Roca says that folks with sleep
apnea have uncharacteristically high levels of leptin.
What's more, when their apnea is treated, leptin levels drop -- and somehow that
helps them to lose weight.
"I've had about thirty patients who, when successfully treated for their sleep
apnea were able to lose weight -- possibly because they had more energy, so
they were more active and they just ate less," says Breus.
So why does low leptin seem to cause weight gain in some folks while allowing
others to lose weight? One theory says that it may not be the level of this
hormone that matters so much as a person's individual response to it. In much
the same way that obese people can become resistant to insulin, folks with
apnea may be resistant to the fullness signal that leptin sends to the brain.
"It's like the body is trying to tell them to stop eating, but their brain just
isn't getting the message," says Breus.
Another theory: The overall response to leptin may be more individual than we
think. Experts say our environment, dietary habits, exercise patterns, personal
stress levels, and particularly our genetics may all influence the production
of leptin and ghrelin, as well as our response to them.
The fact that we just don't know causes at least some experts to view all
the research on sleep and weight with a cautious or skeptical eye.
"There is a serious challenge to the closing of the loop. That isn't to say that
what we know about leptin and ghrelin is not important, or that when we finally
do understand it that it won't be crystal clear -- but right now it just
isn't," Rapoport tells WebMD.
Breus agrees: "I think we are likely to find that bad sleep matters but that
it's likely to be bad sleep plus some other problems. I don't think we know
what they are yet."
Sleep: You Can't Lose
Until doctors do know more, most experts agree that if you are dieting, logging
in a few extra hours of sleep a week is not a bad idea, particularly if you get
six hours of sleep or less a night. You may just discover that you aren't as
hungry, or that you have lessened your craving for sugary, calorie-dense foods.
"One thing I have seen is that once a person is not as tired, they don't need to
rely on sweet foods and high carbohydrate snacks to keep them awake -- and that
automatically translates into eating fewer calories," says Breus.
If, on the other hand, you already sleep a lot, or you increase your sleep and
feel even more tired, you should talk to your doctor. Experts say you may be
one of the thousands of people with undiagnosed sleep apnea.
Says Roca: "As research continues, more and more data comes to the forefront to
suggest that you simply can't cut back on sleep without paying some price."
By Colette Bouchez
Published Friday, February 04, 2005.
Reviewed By Kathleen Zelman, MPH, RD, July 25, 2007.
Medically updated July 25, 2007.
SOURCES: David Rapoport, MD, associate professor and director of the Sleep
Medicine Program, NYU School of Medicine, New York City. Michael Breus, PhD,
Atlanta School of Sleep Medicine; clinical director of The Sleep Disorder
Centers of Southeastern Lung Care, Atlanta. Dominic Roca, MD, director of the
Connecticut Center for Sleep Medicine, Stamford Hospital. Annals of Internal
Medicine, 2004; vol 141: pp 846-850. PLOS Medicine, December
2004; vol 1. Journal of Clinical Endocrinology and Metabolism; vol 89:
pp 5762-5771. American Journal of Physiology -- Heart and Circulatory
Physiology, July 2000; vol 279: pp H234-H237.
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