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Item #15
Thinner,
Fitter Teens Less Likely to Have Precursor to Diabetes
Fatness
and fitness contribute independently to changes in insulin sensitivity
that could predispose teenagers to diabetes.
That
was reported at the American Heart Association’s 43rd Annual
Conference on Cardiovascular Disease Epidemiology and Prevention by
the Medical College of Georgia researchers.
Insulin
sensitivity is a measure of how well the body responds to the hormone
insulin which is needed to transport carbohydrates from the blood into
cells where they can be turned into energy.
Lead
author Dr. Bernard Gutin, professor of pediatrics and physiology at
MCG in Augusta stated that, “This is the first study to look at
these questions in a large group of adolescents that includes both
blacks and whites and males and females.”
The
researchers found that race and gender were related to insulin
sensitivity, which was highest among white girls and lowest among
black girls.
They
studied 289 teenagers ages 14-18 recruited from high schools in the
Augusta area.
Insulin
sensitivity was estimated using fasting blood tests for insulin and
glucose (the blood sugar transported into cells by insulin).
Cardiovascular fitness was measured by calculating how much oxygen
each subject used when a brisk, uphill walk on a treadmill brought
their heart rate to 170 beats per minute. The researchers also
measured body composition (the amount of body fat vs. fat-free mass),
and waist circumference, an indication of abdominal fat.
They
found that boys had higher cardiovascular fitness than girls, as well
as lower percent body fat. When the researchers controlled for race
and gender, they found that higher cardiovascular fitness and lower
body fat were independently associated with greater insulin
sensitivity.
That
finding suggests that improving fitness or reducing body fat could
protect high-risk children, Dr. Gutin says. “This is an important
finding because some people think that it is really body fat that is
the critical factor in the development of diabetes,” he says. “We
found that it was certainly very important, but that even after
adjusting for it, fitness still made an independent contribution.”
The
researchers chose the 14-18-year-old age group because they hoped to
study the early development of diabetes while avoiding changes in
insulin sensitivity during puberty that might have skewed the results.
The
mystery of the early course of diabetes is getting a lot of attention
now because the last two decades have seen an explosion in the number
of cases of teenagers with type 2 diabetes, a condition once called
“adult-onset” diabetes because it was so rare in young people, he
says.
Low
insulin sensitivity, also called insulin resistance, is not diabetes,
although it often is a prelude to the disease. In people with low
insulin sensitivity, the body makes insulin but is unable to use it
efficiently to transport glucose out of the blood, requiring a
greater-than-average amount of insulin to transport an average amount
of glucose. When the pancreas cannot keep up with demands for extra
insulin, glucose levels begin to creep up toward the diabetic range.
That’s why it is important to measure blood levels of both glucose
and insulin in order to study how diabetes develops, Dr. Gutin says.
Dr.
Gutin recommends parents schedule at least an hour of sweat-inducing
exercise into their children’s afternoon activities. He says the
study findings are important because they indicate that “every child
can benefit from higher fitness and lower fatness. Even people who are
chubby can improve their metabolism by having good fitness.”
The
research was supported by grants from the National Heart, Lung, and
Blood Institute of the National Institutes of Health.
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