title: Relation of birth weight, body mass index, and change in size from birth to adulthood to insulin resistance in a female twin cohort.
abstract: OBJECTIVE
  Because an adverse intrauterine environment is thought to induce insulin resistance, our objective was to investigate the relationships between birth weight, BMI, and change in body size over the life course and insulin resistance. SETTING, DESIGN, AND PARTICIPANTS: We conducted a cross-sectional study in a cohort of 1194 female twins aged 18-74 yr. The relationship between birth weight and insulin resistance was analyzed using a regression method allowing for a simultaneous estimation of within- and between-pair influences. The approach allows the influence of individual fetal nutrition on adult insulin resistance to be distinguished from effects that are mediated by confounding factors in the maternal environment.
  
  
  METHODS
  Insulin resistance was measured by the homeostasis model assessment.
  
  
  RESULTS
  Individual level regression analyses showed no significant relationship between birth weight and insulin resistance. There was a significant positive relationship between insulin resistance and current body mass index (BMI) (a 26% increase in insulin resistance per sd increase in BMI; confidence interval, 22.6-29.5%). This significant relationship was accounted for in equal parts by individual-specific effects and by confounding factors in the shared environment of the twins. The relationship with birth weight became significant only after adjustment for BMI and was mediated only through between-pair differences.
  
  
  CONCLUSIONS
  These results suggest that insulin resistance is influenced more by current body size than birth weight and that postnatal growth is potentially more important than fetal growth in the subsequent development of insulin resistance.
authors.affiliation: School of Medicine, Health Policy, and Practice, University of East Anglia, Norwich NR4 7JT, United Kingdom. p.skidmore@uea.ac.uk
authors.forename: Paula M L
authors.initials: PM
authors.lastname: Skidmore
authors.forename: Aedin
authors.initials: A
authors.lastname: Cassidy
authors.forename: Ramasamyiyer
authors.initials: R
authors.lastname: Swaminathan
authors.forename: J Brent
authors.initials: JB
authors.lastname: Richards
authors.forename: Tim D
authors.initials: TD
authors.lastname: Spector
authors.forename: Alex J
authors.initials: AJ
authors.lastname: MacGregor
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001724:Birth Weight / Q000502:physiology*; D001786:Blood Glucose / Q000378:metabolism; D015992:Body Mass Index; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D007328:Insulin / Q000097:blood; D007333:Insulin Resistance / Q000502:physiology*; D016014:Linear Models; D008875:Middle Aged; D014429:Twins, Dizygotic / Q000502:physiology*; D014430:Twins, Monozygotic / Q000502:physiology*
chemical_list: D001786:Blood Glucose; D007328:Insulin