title: Physical activity, diet and gene-environment interactions in relation to body mass index and waist circumference: the Swedish young male twins study.
abstract: OBJECTIVE
  The aim of the present study was to examine the relationships between genetic susceptibility to obesity, physical activity (PA), dietary fibre, sugar and fat intakes and 4-year changes in body mass index (BMI) and attained waist circumference (WC) in a cohort of 287 monozygotic and 189 dizygotic young adult male twin pairs. Increased knowledge about interactions between genes and environment may provide insight into why some individuals are more prone to obesity than others.
  
  
  METHODS
  Information about PA, BMI, dietary habits, WC and potential confounders was collected by questionnaire in 1998 and 2002. The cohort data were analysed by mixed linear models.
  
  
  RESULTS
  Twins with low PA attained larger WC than twins with high PA (difference 2.5 cm; 95% confidence interval (CI) 1.3, 3.6). The twins with the lowest fibre intake were found to have attained the highest WC and to have increased most in BMI (difference between highest and lowest fibre intakes: 1.6 cm, 95% CI 0.4, 2.9 and 0.45 kg m(-2), 95% CI 0.15, 0.76, respectively). Furthermore, our results suggested the presence of interactions so that twins with genetic susceptibility to obesity were more prone to have larger WC if sedentary than twins without genetic susceptibility.
  
  
  CONCLUSIONS
  PA and a diet rich in fibre may be protective against weight gain among younger adult men. An interaction between PA, genes and attained WC is a novel finding which needs confirmation by other studies.
authors.affiliation: Child and Adolescent Public Health Epidemiology Group, Department of Public Health Sciences, Karolinska Institute, Norrbacka, SE-171 76 Stockholm, Sweden.
authors.forename: Nina
authors.initials: N
authors.lastname: Karnehed
authors.forename: Per
authors.initials: P
authors.lastname: Tynelius
authors.forename: Berit L
authors.initials: BL
authors.lastname: Heitmann
authors.forename: Finn
authors.initials: F
authors.lastname: Rasmussen
mesh_terms: D000328:Adult; D015992:Body Mass Index; D015331:Cohort Studies; D004032:Diet; D004034:Diet Surveys; D004043:Dietary Fiber / Q000008:administration & dosage; D015444:Exercise / Q000502:physiology*; D005247:Feeding Behavior; D020022:Genetic Predisposition to Disease; D006801:Humans; D016014:Linear Models; D008297:Male; D009765:Obesity / Q000453:epidemiology* / Q000235:genetics*; D011795:Surveys and Questionnaires; D013548:Sweden; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic; D049629:Waist-Hip Ratio; D015430:Weight Gain / Q000235:genetics