The relationship between utilitarian walking, utilitarian cycling, and body mass index in a population based cohort study of adults: Comparing random intercepts and fixed effects models

•Lack of cohort studies on active transportation and body mass index (BMI)•Assumed negative relationship between active transportation and BMI•Transportation walking is not associated with lower BMI over time.•Unclear relationship between transportation cycling and BMI over time•Active transportation interventions may have small influence on BMI.

ObjectiveTo examine associations between utilitarian walking, utilitarian cycling, leisure time physical activity and body mass index (BMI).MethodsParticipants from the National Population Health Survey (NPHS) of Statistics Canada were interviewed by telephone every two years from 1994 to 2010. Analysis includes data from 6894 living participants aged 18-64 years. Fixed effects and random intercepts models examined the association between BMI, utilitarian walking, and utilitarian cycling, controlling for behavioral and sociodemographic factors.ResultsThe final adjusted fixed effects models showed no significant relationship between utilitarian walking and BMI. In the unbalanced sample utilitarian cycling for 1 to 5 h per week (b = − 0.15, 95% CI: − 0.28 to − 0.02), and more than 5 h per week (b = − 0.22, 95% CI: − 0.44 to 0.00) was significantly associated with BMI over time. In the fully balanced sample utilitarian cycling for 1 to 5 h per week (b = − 0.12, 95% CI: − 0.27 to 0.03), more than 5 h per week (b = − 0.16, 95% CI: − 0.45 to 0.13) was not significantly associated with BMI over time.ConclusionThe results suggest that utilitarian walking is not related to BMI. The relationship between utilitarian cycling and BMI is less clear.