title: Impact of changes in mode of travel to work on changes in body mass index: evidence from the British Household Panel Survey.
abstract: BACKGROUND
  Active commuting is associated with various health benefits, but little is known about its causal relationship with body mass index (BMI).
  
  
  METHODS
  We used cohort data from three consecutive annual waves of the British Household Panel Survey, a longitudinal study of nationally representative households, in 2004/2005 (n=15,791), 2005/2006 and 2006/2007. Participants selected for the analyses (n=4056) reported their usual main mode of travel to work at each time point. Self-reported height and weight were used to derive BMI at baseline and after 2 years. Multivariable linear regression analyses were used to assess associations between switching to and from active modes of travel (over 1 and 2 years) and change in BMI (over 2 years) and to assess dose-response relationships.
  
  
  RESULTS
  After adjustment for socioeconomic and health-related covariates, the first analysis (n=3269) showed that switching from private motor transport to active travel or public transport (n=179) was associated with a significant reduction in BMI compared with continued private motor vehicle use (n=3090; -0.32 kg/m(2), 95% CI -0.60 to -0.05). Larger adjusted effect sizes were associated with switching to active travel (n=109; -0.45 kg/m(2), -0.78 to -0.11), particularly among those who switched within the first year and those with the longest journeys. The second analysis (n=787) showed that switching from active travel or public transport to private motor transport was associated with a significant increase in BMI (0.34 kg/m(2), 0.05 to 0.64).
  
  
  CONCLUSIONS
  Interventions to enable commuters to switch from private motor transport to more active modes of travel could contribute to reducing population mean BMI.
authors.affiliation: Health Economics Group and UKCRC Centre for Diet and Activity Research (CEDAR), Norwich Medical School, University of East Anglia, Norwich, UK.
authors.forename: Adam
authors.initials: A
authors.lastname: Martin
authors.affiliation: MRC Epidemiology Unit and UKCRC Centre for Diet and Activity Research (CEDAR), University of Cambridge, Cambridge, UK.
authors.forename: Jenna
authors.initials: J
authors.lastname: Panter
authors.affiliation: Health Economics Group and UKCRC Centre for Diet and Activity Research (CEDAR), Norwich Medical School, University of East Anglia, Norwich, UK Centre for Health Economics, University of York, York, UK.
authors.forename: Marc
authors.initials: M
authors.lastname: Suhrcke
authors.affiliation: MRC Epidemiology Unit and UKCRC Centre for Diet and Activity Research (CEDAR), University of Cambridge, Cambridge, UK.
authors.forename: David
authors.initials: D
authors.lastname: Ogilvie
mesh_terms: D000328:Adult; D001334:Automobile Driving / Q000706:statistics & numerical data; D001642:Bicycling / Q000502:physiology* / Q000706:statistics & numerical data; D015992:Body Mass Index; D004651:Employment; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D015999:Multivariate Analysis; D009765:Obesity / Q000517:prevention & control*; D012959:Socioeconomic Factors; D011795:Surveys and Questionnaires; D014186:Transportation / Q000379:methods* / Q000706:statistics & numerical data; D006113:United Kingdom; D016138:Walking / Q000502:physiology* / Q000706:statistics & numerical data
keywords: OBESITY; PHYSICAL ACTIVITY; WORKPLACE