title: Authors' reply to McGregor and Foley.
authors.affiliation: Department of Social and Environmental Health Research, London School of Hygiene and Tropical Medicine, London WC1H 9SH, UK ellen.flint@lshtm.ac.uk.
authors.forename: Ellen
authors.initials: E
authors.lastname: Flint
authors.affiliation: Department of Social and Environmental Health Research, London School of Hygiene and Tropical Medicine, London WC1H 9SH, UK.
authors.forename: Steven
authors.initials: S
authors.lastname: Cummins
authors.affiliation: ESRC International Centre for Lifecourse Studies in Society and Health, Research Department of Epidemiology and Public Health, University College London, London WC1E 6BT, UK.
authors.forename: Amanda
authors.initials: A
authors.lastname: Sacker
mesh_terms: D001642:Bicycling / Q000706:statistics & numerical data*; D050218:Body Fat Distribution; D015992:Body Mass Index; D005260:Female; D006801:Humans; D008297:Male; D014186:Transportation / Q000379:methods* / Q000706:statistics & numerical data*; D016138:Walking / Q000706:statistics & numerical data*