title: Association of physical activity and body composition with insulin sensitivity in a community sample of adolescents.
abstract: OBJECTIVE
  To examine how body composition and physical activity are related to insulin sensitivity and secretion in adolescents.
  
  
  METHODS
  Cross-sectional.
  
  
  METHODS
  Baltimore, Maryland.
  
  
  METHODS
  Fifty-six healthy adolescents (34 boys and 22 girls; mean [SD] age, 13.3 [1.3] years; 95% were African American) who had been recruited at infancy from a health care clinic serving a low-income, urban community. Main Exposures Physical activity was measured for 5 to 7 days by a uniaxial accelerometer placed on the right ankle. Proportion of time spent in play-equivalent physical activity (PEPA) was defined as 1800 or more counts per minute. Body mass index (BMI) (calculated as weight in kilograms divided by height in meters squared) was converted to an age- and sex-specific z score.
  
  
  METHODS
  Insulin sensitivity, insulin secretion, and disposition index calculated from a fasting oral glucose tolerance test.
  
  
  RESULTS
  Thirty-nine percent of the adolescents had a BMI in the 85th percentile or higher; half of those were overweight (BMI > or = 95th percentile). Play-equivalent physical activity and BMI z score were not correlated. In multivariate analyses, BMI z score and time spent in PEPA together explained 21% of the variance in insulin sensitivity and 18% in insulin secretion. Independent of each other, high BMI z score and low proportion of PEPA were significantly associated with low insulin sensitivity (partial r(2) = 0.14 and 0.10, respectively) and high insulin secretion (partial r(2) = 0.10 and 0.10, respectively), but not with disposition index.
  
  
  CONCLUSIONS
  In a cohort of urban, predominantly African American adolescents, both body composition and physical activity were independently associated with insulin sensitivity. At this point, insulin secretion is appropriately regulated.
authors.affiliation: Department of Medicine, University of Maryland School of Medicine, Baltimore, Maryland, USA. ssnitker@medicine.umaryland.edu
authors.forename: Soren
authors.initials: S
authors.lastname: Snitker
authors.forename: Katherine Y
authors.initials: KY
authors.lastname: Le
authors.forename: Erin
authors.initials: E
authors.lastname: Hager
authors.forename: Benjamin
authors.initials: B
authors.lastname: Caballero
authors.forename: Maureen M
authors.initials: MM
authors.lastname: Black
mesh_terms: D000054:Acceleration; D050154:Adiposity; D000293:Adolescent; D001741:Black or African American / Q000706:statistics & numerical data*; D000886:Anthropometry; D015142:Baltimore / Q000453:epidemiology; D001823:Body Composition / Q000502:physiology*; D015992:Body Mass Index; D003151:Community Health Centers; D003430:Cross-Sectional Studies; D005260:Female; D005951:Glucose Tolerance Test; D006305:Health Status Indicators; D006801:Humans; D007328:Insulin / Q000378:metabolism*; D007333:Insulin Resistance / Q000208:ethnology / Q000502:physiology*; D000078790:Insulin Secretion; D008297:Male; D009043:Motor Activity / Q000502:physiology*; D009765:Obesity / Q000453:epidemiology / Q000208:ethnology; D012959:Socioeconomic Factors; D014504:Urban Health / Q000706:statistics & numerical data*
chemical_list: D007328:Insulin