The Medical College of Georgia finding was presented March 7 at the American Heart Association's annual conference on cardiovascular disease epidemiology and prevention in Miami.
The study included 289 teenagers aged 14 to 18 from high schools near Augusta, Ga. Their insulin sensitivity was estimated using fasting blood tests for insulin and glucose (blood sugar).
Cardiovascular fitness was measured by determining how much oxygen each teen used when his heart rate reached 170 beats a minute while walking on a treadmill. The researchers also collected information about the teens' body composition (amount of fat versus fat-free mass) and their abdominal fat.
The study found lower body fat and higher cardiovascular fitness were associated with greater insulin sensitivity, which is a measure of how well the body responds to insulin.
Insulin is a hormone that carries carbohydrates from the blood into cells. The cells turn the carbohydrates into energy.
High insulin sensitivity means that the body responds well to insulin. Low insulin sensitivity, which is also called insulin resistance, is often a precursor to diabetes.
This study also found that race and gender affected insulin sensitivity. It was highest among white girls and lowest among black girls.
The finding that lower body fat and better cardiovascular fitness are associated with higher insulin sensitivity suggests that improving fitness and reducing body fat may be ways to protect children who are high risk of developing diabetes.
Here's where you can learn more about insulin resistance.