Combined associations of takeaway food availability and walkability with adiposity: Cross-sectional and longitudinal analyses.

Background: Diet and physical activity are important determinants of energy balance, body weight and chronic health conditions. Peoples' health and behaviour are shaped by their environment. For example, the availability of unhealthy takeaway food in residential neighbourhoods and the ability to easily walk to a range of local destinations (high "walkability") influence diets and physical activity levels. Most existing evidence on the associations between residential neighbourhood and adiposity is cross-sectional and examines either walkability or takeaway availability, but not both in combination.We examined the cross-sectional and longitudinal associations of residential neighbourhood walkability and takeaway food availability with markers of adiposity separately and combined.

Methods: With data from the Fenland Study (Cambridgeshire, UK; n = 12,435), we used linear regression to estimate associations for walkability and takeaway availability separately and in mutually adjusted models, in addition to combining both into a measure of neighbourhood supportiveness for active living and healthy eating. Objective measures of BMI were examined cross-sectionally at baseline (2005-2015) and as change between baseline and follow-up (2014-2020). Additional outcomes (percentage body fat, waist circumference and hip circumference) were also examined both cross-sectionally and longitudinally.

Results: Complete case analyses indicated that neighbourhoods with greater walkability and lower takeaway availability were associated with lower BMI (n = 10,607) and more favourable trends over time (n = 5508). For example, compared with the lowest exposure group (Q1), Q4 of walkability and takeaway food availability was associated with a difference in BMI of -0.69 kg/m (95% CI = -1.09 to -0.29) and 0.99 kg/m (95% CI = 0.58 to 1.39) respectively. These associations were more consistent when both neighbourhood measures were included in mutually adjusted models. The combined supportiveness measure was associated with lower BMI. High walkability and low takeaway availability were also associated with lower body fat percentage, waist circumference and hip circumference.

Conclusions: These findings are consistent with the residential environment having a role in shaping people's health and behaviour. Living in an area that supports walking and cycling and affords less access to unhealthy food may support people to maintain a healthy lifestyle. It was important to consider walkability and takeaway food availability together because to examine them separately risks unobserved confounding by the other. Future research could incorporate additional environmental measures, especially those likely to be correlated.