title: Direction of causality between body fat and insulin resistance in children--a longitudinal study (EarlyBird 51).
abstract: OBJECTIVE
  To investigate the direction of causality in the association between adiposity and insulin resistance in children.
  
  
  METHODS
  Body composition by DEXA, and insulin resistance by HOMA-2 IR were measured annually in 238 children aged from 7-13 years. Longitudinal modelling was used to establish whether baseline and/or trends in adiposity were associated with change in IR or whether, conversely, baseline and/or trends in IR were associated with change in adiposity.
  
  
  RESULTS
  Baseline adiposity was associated with change in IR in the short-term (p < 0.001) but less so in the long-term (p < 0.09) in both genders. Baseline IR was not associated with short-term change in adiposity in either gender (p > 0.42). In the long-term, baseline IR appeared to be positively associated with change in adiposity in boys (p = 0.02) but inversely associated with change in adiposity (the higher the baseline IR, the lower the gain in %fat) in girls (p < 0.001).
  
  
  CONCLUSIONS
  The dominant direction of causality appears to be from adiposity to insulin resistance. In boys, adiposity appears to be both a cause and an effect of IR in the long term. In girls, however, higher insulin resistance appeared to limit further gain in body fat in the long term, an observation consistent with insulin desensitization as an adaptive response to weight gain.
authors.affiliation: Department of Endocrinology & Metabolism, Peninsula Medical School, Plymouth campus, UK.
authors.forename: Joanne
authors.initials: J
authors.lastname: Hosking
authors.forename: Brad S
authors.initials: BS
authors.lastname: Metcalf
authors.forename: Alison N
authors.initials: AN
authors.lastname: Jeffery
authors.forename: Linda D
authors.initials: LD
authors.lastname: Voss
authors.forename: Terence J
authors.initials: TJ
authors.lastname: Wilkin
mesh_terms: D000273:Adipose Tissue / Q000378:metabolism; D050154:Adiposity; D000293:Adolescent; D015992:Body Mass Index; D002648:Child; D015331:Cohort Studies; D005260:Female; D006801:Humans; D007333:Insulin Resistance; D008137:Longitudinal Studies; D008297:Male; D011446:Prospective Studies; D012727:Sex Characteristics