Obesity: Is Lack
of Sleep a Factor?
Jun 30, 2005
Ample scientific evidence supports the value of a good
night's sleep, and the latest findings suggest that
if you don't get enough sleep you may tend to overeat.
This, in turn, may contribute to obesity.
Far-fetched? Maybe not.
The research on sleep is tied to other research on the
role of hormones and genetics and their impact on obesity.
A hot area of research over the past decade is leptin,
a hormone produced in adipose tissue that stores fat
in the body. Leptin is secreted into the blood and makes
its way to the brain where it blunts the appetite.
The more fat you have, the more leptin you produce and
secrete. Thus, leptin serves as a feedback device telling
your body that it has plenty of stored energy (body
fat) and it doesn't need to store more.
Individuals who are genetically deficient in leptin
tend to become massively obese. Studies of such individuals
have shown that when leptin is administered, their food
intake drops.
What's more, their stores of body fat are mobilized,
meaning the body increases its use of body fat as fuel,
and, eventually, their weight moves down nearer normal
levels.
In the gastrointestinal tract, the hormone ghrelin also
is attracting attention. Ghrelin exerts the opposite
effect as leptin; it stimulates food intake.
Ghrelin levels tend to be low in the obese, suggesting
that the obese body doesn't need to be stimulated hormonally
to consume more food.
In some obese individuals, however, ghrelin levels may
be high and promote gluttony. This condition is called
Prader-Willi syndrome.
With the exception of those with Prader-Willi syndrome,
the low ghrelin levels associated with obesity suggest
that "automatic" eating (snacking in front
of the TV, etc.), poor food choices and lack of physical
activity are more responsible for obesity than this
hormone.
The hormone cortisol also may be a key player. Cortisol
typically is produced in the outer layer of the adrenal
glands. However, inactive cortisone in fat storage cells
can be activated to also produce cortisol.
In turn, cortisol can stimulate deposition of deep body
fat around the organs in the abdominal region. In addition,
excess cortisol can stimulate production of more fat
storage sites. These problems are most typical in menopausal
females.
Other similar mechanism are now being studied, and results
suggest strongly that in many obese individuals it's
not just the bacon cheeseburgers, super-sized fries
and soft drinks, plus a lethargic lifestyle, that are
causing the problem, although clearly they are contributors.
Indeed, there may be deficient hormonal physiologic
regulators that promote obesity, as much as or more
than a lack of will power. So, where does lack of sleep
come into play?
Sleep deprivation
Recent studies on the impact of sleep deprivation are
intriguing. In subjects limited to only four hours'
sleep per night for two days, levels of leptin decreased
and ghrelin increased.
This means that with less leptin the blunting influence
on the appetite is reduced. And with more ghrelin, the
appetite is increased. Conversely, when subjects were
provided with a full night of restful sleep, these hormone
trends were reversed.
We also know that sleep deprivation is one of the most
stressful conditions you can impose on the body, and
cortisol is a stress hormone.
Thus, it's possible that sleep
deprivation could increase cortisol release from the
adrenal glands, which, when combined with cortisol produced
in fat storage cells, could increase fat storage sites.
When there are more sites available to store fat, the
body becomes better at it, and obesity increases.
What's more, many obese individuals are "stress
eaters." They resort to food as comfort in times
of stress. Is this purely psychological, or does it
tie in with the hormonal responses discussed above that
are associated with lack of adequate sleep? Hard to
say. More research is needed.
The bottom line
These latest research findings reinforce the multifaceted
nature of obesity. But please don't leap to the conclusion
that those extra pounds around your midsection or on
your hips, thighs and buttocks are mainly from lack
of sleep.
Rather, view these research findings as additional pieces
of the puzzle that can help you plan a comprehensive
approach to reducing body fat and keeping it off.
My typical advice of making better food choices, reducing
portion sizes and being physically active on a daily
basis still apply to all of us.
In addition, throw in the habit of getting a good night's
sleep and you will have all of the bases covered --
at least all of the bases we are aware of at the present
time.
"The Body Shop" runs Thursdays. Bryant Stamford
is professor and director of the Health Promotion Center
at the University of Louisville and co-host of "HealthWorks"
on WFPL radio. If you have questions or suggestions,
go to his Web site at DrBryantStamford.com. Or address
questions to "The Body Shop," The Courier-Journal,
P.O. Box 740031, Louisville, KY 40201-7431.
Source: http://www.courier-journal.com
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