title: Association of IGF axis hormones with waist-to-hip ratio varies by physical activity.
abstract: OBJECTIVE
  Insulin-like growth factor (IGF) axis hormones are associated with multiple chronic diseases. Reports of the relationship between adiposity and IGF-axis hormones vary widely. This study hypothesized that physical activity levels modify the association of IGF axis hormones with adiposity.
  
  
  METHODS
  Data from NHANES III were used to assess whether associations of adiposity, namely waist-to-hip ratio (WHR), with IGF axis hormones varied according to physical activity.
  
  
  RESULTS
  Among those in the lowest physical activity quintile, WHR had a substantive inverse association: bioavailable IGF-I was 16% lower among those in the highest versus the lowest WHR quintiles among the least active subjects (p<0.001). By comparison, among those in the highest physical activity quintile, IGF-I did not vary by WHR.
  
  
  CONCLUSIONS
  The association of bioavailable IGF-1 with central adiposity differs among active versus inactive adults in the U.S.A. This has relevance to understanding previously reported benefits of physical activity among overweight individuals.
authors.affiliation: Center for Clinical Epidemiology and Biostatistics, University of Pennsylvania School of Medicine, 903 Blockley Hall, 423 Guardian Drive, Philadelphia, PA 19104-6021, USA. Schmitz@mail.med.upenn.edu
authors.forename: Kathryn H
authors.initials: KH
authors.lastname: Schmitz
authors.forename: Dawei
authors.initials: D
authors.lastname: Xie
authors.forename: Valerie
authors.initials: V
authors.lastname: Teal
authors.forename: Rachel
authors.initials: R
authors.lastname: Ballard-Barbash
authors.forename: David
authors.initials: D
authors.lastname: Berrigan
mesh_terms: D050154:Adiposity; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015992:Body Mass Index; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000097:blood*; D007334:Insulin-Like Growth Factor I / Q000032:analysis*; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D009749:Nutrition Surveys; D014481:United States; D049629:Waist-Hip Ratio; D055815:Young Adult
chemical_list: D018972:Insulin-Like Growth Factor Binding Protein 3; D007334:Insulin-Like Growth Factor I