Physical Activity, Cardiovascular Fitness, and Insulin Sensitivity Among U.S. Adolescents

The National Health and Nutrition Examination Survey, 1999–2002

  1. Giuseppina Imperatore, MD, PHD1,
  2. Yiling J. Cheng, MD, PHD1,
  3. Desmond E. Williams, MD, PHD1,
  4. Janet Fulton, PHD2 and
  5. Edward W. Gregg, PHD1
  1. 1Division of Diabetes Translation, National Center for Chronic Disease Prevention and Health Promotion, Centers for Disease Control and Prevention, Atlanta, Georgia
  2. 2Division of Nutrition and Physical Activity, National Center for Chronic Disease Prevention and Health Promotion, Centers for Disease Control and Prevention, Atlanta, Georgia
  1. Address correspondence and reprint requests to Dr. Giuseppina Imperatore, Division of Diabetes Translation, CDC, 4770 Buford Highway, NE MS-K10, Atlanta, GA 30341. E-mail: gai5{at}


OBJECTIVE—The purpose of this study was to examine the association of physical activity and cardiovascular fitness (CVF) with insulin sensitivity in a nationally representative sample of U.S. youth.

RESEARCH DESIGN AND METHODS—The study included 1,783 U.S. adolescents (11% Mexican American, 14% non-Hispanic black, 63% non-Hispanic white, and 12% other) aged 12–19 years who were examined in the 1999–2002 National Health and Nutrition Examination Survey. Physical activity was assessed by questionnaire and expressed in units of MET hours per week. Predicted maximal oxygen uptake (Vo2max, expressed in milliliters per kilogram of body weight per minute), a measure of CVF, was determined by a submaximal multistage treadmill test. Insulin sensitivity was defined by the Quantitative Insulin Sensitivity Check Index.

RESULTS—Boys were more likely than girls to be highly active (≥30 MET h/week; 51 vs. 37%, P < 0.001) and had higher levels of CVF (mean Vo2max 47 vs. 39 ml · kg−1 · min−1, P < 0.001). Sex-specific multiple regression models controlled for age, race/ethnicity, and BMI showed that in boys, high levels of physical activity and high levels of CVF were significantly and positively associated with insulin sensitivity (β = 0.84, P < 0.001 and β = 0.82, P = 0.01, respectively). Among girls, insulin sensitivity was not significantly associated with physical activity or with CVF but was inversely and significantly associated with BMI.

CONCLUSIONS—Increasing physical activity and CVF may have an independent effect of improving insulin sensitivity among boys. For girls, the primary role of physical activity may be in weight maintenance.


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    A table elsewhere in this issue shows conventional and Système International (SI) units and conversion factors for many substances.

    • Accepted April 18, 2006.
    • Received February 22, 2006.
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