title: Physical activity attenuates the effect of low birth weight on insulin resistance in adolescents: findings from two observational studies.
abstract: OBJECTIVE
  To examine whether physical activity influences the association between birth weight and insulin resistance in adolescents.
  
  
  METHODS
  The study comprised adolescents who participated in two cross-sectional studies: the Healthy Lifestyle in Europe by Nutrition in Adolescence (HELENA) study (n = 520, mean age = 14.6 years) and the Swedish part of the European Youth Heart Study (EYHS) (n = 269, mean age = 15.6 years). Participants had valid data on birth weight (parental recall), BMI, sexual maturation, maternal education, breastfeeding, physical activity (accelerometry, counts/minute), fasting glucose, and insulin. Insulin resistance was assessed by homeostasis model assessment-insulin resistance (HOMA-IR). Maternal education level and breastfeeding duration were reported by the mothers.
  
  
  RESULTS
  There was a significant interaction of physical activity in the association between birth weight and HOMA-IR (logarithmically transformed) in both the HELENA study and the EYHS (P = 0.05 and P = 0.03, respectively), after adjusting for sex, age, sexual maturation, BMI, maternal education level, and breastfeeding duration. Stratified analyses by physical activity levels (below/above median) showed a borderline inverse association between birth weight and HOMA-IR in the low-active group (standardized β = -0.094, P = 0.09, and standardized β = -0.156, P = 0.06, for HELENA and EYHS, respectively), whereas no evidence of association was found in the high-active group (standardized β = -0.031, P = 0.62, and standardized β = 0.053, P = 0.55, for HELENA and EYHS, respectively).
  
  
  CONCLUSIONS
  Higher levels of physical activity may attenuate the adverse effects of low birth weight on insulin sensitivity in adolescents. More observational data, from larger and more powerful studies, are required to test these findings.
authors.affiliation: Unit for Preventive Nutrition, Department of Biosciences and Nutrition, Karolinska Institutet, Huddinge, Sweden. ortegaf@ugr.es
authors.forename: Francisco B
authors.initials: FB
authors.lastname: Ortega
authors.forename: Jonatan R
authors.initials: JR
authors.lastname: Ruiz
authors.forename: Anita
authors.initials: A
authors.lastname: Hurtig-Wennlöf
authors.forename: Aline
authors.initials: A
authors.lastname: Meirhaeghe
authors.forename: Marcela
authors.initials: M
authors.lastname: González-Gross
authors.forename: Luis A
authors.initials: LA
authors.lastname: Moreno
authors.forename: Dénes
authors.initials: D
authors.lastname: Molnar
authors.forename: Anthony
authors.initials: A
authors.lastname: Kafatos
authors.forename: Frederic
authors.initials: F
authors.lastname: Gottrand
authors.forename: Kurt
authors.initials: K
authors.lastname: Widhalm
authors.forename: Idoia
authors.initials: I
authors.lastname: Labayen
authors.forename: Michael
authors.initials: M
authors.lastname: Sjöström
mesh_terms: D000293:Adolescent; D003430:Cross-Sectional Studies; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D007230:Infant, Low Birth Weight / Q000502:physiology*; D007231:Infant, Newborn; D007333:Insulin Resistance / Q000502:physiology*; D008297:Male