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Kids who skimp on sleep tend to be fatter
Nov 07, 2007: While the connection between a child's weight and the amount of sleep that child
gets may not be immediately apparent, new research has found a strong
correlation between the two.
Sixth-graders who averaged less than 8.5
hours of sleep a night had a 23 percent rate of obesity, while their well-rested
peers who averaged more than 9.25 hours of sleep had an obesity rate of just 12
percent, according to a new study.
"We found that children who got less
sleep were more likely to be obese," said the study's lead author, Dr. Julie
Lumeng, an assistant research scientist at the University of Michigan Center for
Human Growth and Development.
Lumeng said that even after compensating
for other factors, such as the home environment, the link between less sleep and
heavier weight was still apparent.
The study results are published in
the November issue of the journal 'Pediatrics.'
Lumeng said there are
three likely reasons why sleep might affect weight. First, if children don't get
enough sleep at night, they'll be less likely to run around and get exercise
during the day. Second, when kids are tired, they're more irritable and may
reach for junk food to help regulate their mood. And, finally, what Lumeng
called a "hot area for future research" is the possible connection between sleep
and fat metabolism. She said there have been studies done with adults that have
shown that a lack of sleep may disrupt the secretion of hormones involved in
appetite and metabolism, such as leptin and insulin.
The new study
included 785 children who were in third grade at the start of the trial. Most
were white - 81 percent - and half were female.
Parents were interviewed
about their children's sleep habits when the youngsters were in third grade and
then again when they were in sixth grade. The researchers also measured height
and weight. Obesity was defined as having a body mass index (BMI, a ratio of
weight to height) higher than the 5th percentile for age and gender, according
to Lumeng. Eighteen percent of the children were obese in sixth grade.
The researchers also took into account maternal education, race, the
quality of the home environment and parenting skills to see if those factors
affected a child's weight.
No matter what a child weighed in third
grade, too little sleep correlated with being obese in sixth grade. And, short
sleep duration in sixth grade also correlated with excess weight in sixth grade,
according to the study.
Third-graders who got less than nine hours and
45 minutes of sleep a night had an obesity prevalence of about 20 percent, while
those who got more than nine hours and 45 minutes of sleep had obesity rates of
about 12 percent, Lumeng said.
Those who were short-changing sleep in
third grade had 40 percent higher odds of being obese in sixth grade, and
sixth-graders who weren't getting enough sleep were 20 percent more likely to be
obese, compared to their well-rested counterparts.
Lumeng said the
researchers weren't able to find a statistical association between quality of
sleep and obesity. But, she said that without a lab-based sleep study, it's
difficult to objectively assess the quality of sleep, so there may be an
association that this study wasn't able to uncover.
Dr. Stephen Sheldon,
director of the Sleep Medicine Center at Children's Memorial Hospital in
Chicago, said he would've liked to see sleep studies so the researchers could
have known more about the quality of sleep these children were getting, such as
how much REM sleep did they get and how fragmented was the sleep?
But,
he said, the bottom line is that "pediatricians and parents really need to start
paying closer attention to sleep-wake habits. In this society, we put a premium
on being awake, and that premium may hurt us in the long run. Sleep may be as
important as food to our health and well-being," said Sheldon, who's also a
professor of pediatrics at the Northwestern University Feinberg School of
Medicine.
Both Lumeng and Sheldon recommended trying to keep a
consistent sleep schedule. Bedtimes and wake times are both important - for
children and adults. Sheldon said it's usually OK to vary your sleep times a
little bit on the weekend, about an hour or so, but, he cautioned, "Letting you
child sleep till noon or mid-afternoon is inviting trouble."
Lumeng also
recommended that children not have a TV in their bedroom, because it can make it
more difficult to fall asleep. - HealthDay News
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