858. Associations between fast food and physical activity environments and adiposity in mid-life: cross-sectional, observational evidence from UK Biobank
Commentary: Peter Edwards, National Heart Foundation of Australia
It is well established that obesity is strongly linked to a range of chronic diseases, including type 2 diabetes and cardiovascular disease, and contributes substantially to excess morbidity, mortality, and rising health-care costs globally. Across the world, the built environment is considered a strong factor associated with the development of obesity and higher adiposity amongst individuals. This has prompted calls to improve the understanding of how factors of the urban environment influence health, to generate possible public health and solutions and policy to curb rising obesity levels.
In this observational, cross-sectional study, Mason and colleagues examined whether neighbourhood exposure to fast-food outlets and physical activity facilities were associated with adiposity in UK adults. Data was obtained from 21 out of 22 UK Biobank assessment centres across the UK between 2006 and 2010.
Participants were aged between 40–69 years. The physical activity environment for each individual was defined as the number of formal physical activity facilities within a 1km street-network buffer around their place of residence. These facilities included a range of indoor and outdoor facilities designed for sporting and leisure activities, such as gyms, swimming pools, and playing fields. Public parks and cycling paths (unless defined as a sporting facility), were not included. For fast-food outlets, the street-network distance (in metres) from an individual’s residential address to the nearest fast-food outlet, was reported. Three adiposity measures: waist circumference, BMI (calculated from height and weight), and body fat percentage (measured by bioimpedance). Individual descriptives, demographics and socioeconomic status were included as potential confounders.
Overall, the study reported outcomes from sample sizes of 401,917 for waist circumference analyses, 401,435 for BMI analyses, and 395,640 for body fat analyses. In fully adjusted models, adiposity was lower among people with greater access to local physical activity facilities compared with those with fewer facilities near their home. Compared with the reference category (no nearby physical activity facilities), the waist circumference of those with at least six facilities nearby was, on average, 1·22 cm smaller, their BMI was 0·57 kg/m2 lower, and their body fat was 0·81 percentage points lower.
Sex was shown to be a confounder, with gender-stratified models showing modestly larger estimates of effects of both neighbourhood exposures on women's adiposity than on men's. Similarly, in income-stratified models, the inverse association we observed for all income groups was most marked among higher-income households. This is unsurprising given many facilities have costs attached to use.
The results of this study provide evidence to support the theory that increasing access to local physical activity facilities and, possibly, reducing access to fast food close to residential areas has the potential to reduce overweight and obesity at the population level. Policies aimed at modifying residential environments to better facilitate healthy lifestyles seem to be warranted, whilst recognising that such an approach might be more effective in some groups than in others. For example, lobbying local governmental or municipal and private providers of physical activity services, to invest in facilities in or near residential areas, and also to ensure that costs of access are managed to avoid inadvertently widening health inequalities.