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.
Source: Diabetes In Control Dot Com.
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