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Change in commute mode and body-mass index: prospective, longitudinal evidence from UK Biobank

International Journal of Behavioral Nutrition and Physical Activity, 13: 129
The parallel issues of weight gain and a decline in active travel in many countries initiated this study which examined the effects of commuting to work type (active or passive) on body mass index (BMI) over a four year period. Physical activity plays an important role in the prevention of weight gain therefore active commuting to work can achieve health, as well as environmental, benefits to society. The study, published in the prestigious Lancet journal, also examined whether socioeconomic and demographic characteristics predicted switching to or from active commuting and whether switching independently predicts change in BMI and the effects of socioeconomic, demographic, or behavioural factors on any evident changes.

The study had methodological strengths in that it used data from the large scale UK Biobank of volunteers aged 40 to 69 years in 2006, with follow-up data collected at one of the 22 study centres, giving 5861 participant responses which could be used in this study. At the centres, height and weight were objectively measured to derive BMI and the participants were also asked about how they get to and from work, with options categorised whether they commuted solely by car or by ‘active’ modes (walk, public transport or cycle). Multivariate logistic regression models examined change in mode over time in relation to BMI, accounting for other socioeconomic, demographic, or behavioural factors such as education, income and occupational standing and walking.

After an average follow-up period of 4·4 years, statistical modelling revealed that those who transitioned from car to active commuting modes had a statistically significant, although modest, decrease in BMI of –0·30 kg/m² (95% CI –0·47 to –0·13; p=0·0005). A similar BMI increase of 0·32 kg/m² (0·13 to 0·50; p=0·008) was observed among those who transitioned from active to car commuting modes. The only factor determining these changes was household income, where those who had experienced a reduction in income were more likely to switch to active commuting.

These findings highlight how active commuting can make a real difference to weight gain and more efforts to increase adoption of walking, cycling and the use of public transport to travel to would result in clear public health gains.