Expert Opinion

Assessing the impact of physical activity and food environment on obesity

In this blog post, PhD student Matthew Hobbs reflects on the findings of a recent study [1] which suggests increased proximity to green space reduces the likelihood obesity. He also explores his own involvement in research, attempting to assess the impact of the physical activity and food environment on obesity.
What we eat and how active we are plays an important role in determining our risk of gaining weight and becoming obese. Research is increasingly focusing on the role that the immediate environment might have on increasing weight. The physical activity and food environments have been labelled as obesogenic, encouraging convenient access to high calorie food whist discouraging energy expenditure. Recently, Public Health England emphasised the importance of regulating the growth of fast food takeaways and promoting active travel for reducing rates of obesity.

More specifically, green space i.e. public parks is just one aspect of the physical activity environment that may promote physical activity and in turn reduce obesity levels. However, both beneficial and counterintuitive associations have been reported. A more recent study [2] revealed that women in neighbourhoods with over 80% green space had a 10% reduction in risk of overweight (relative risk ratios 0.90 [95% CI: 0.83, 0.97]) and 17% reduction in risk of obesity (0.83 [0.74, 0.94]). Interestingly, no similarly positive association was found in men. This study is amongst the first to report gender differences in the association between green space and obesity.

Whilst this study seems convincing, the wider evidence-base linking the physical activity and food environment to obesity is equivocal. Furthermore, local retail environments and the quality of green space are also likely to have important roles in determining obesity risk. Large systematic reviews [3] have confirmed that, despite many studies, few yielded strong evidence linking the physical activity or food environment to obesity. Furthermore, more powerful research approaches are needed to establish the actual relationships between both the food and physical activity environment and obesity. Currently, we are undertaking several projects in this area.

Our research is currently exploring variations in the availability of the food and physical activity environment by area-level deprivation with local-level analysis across large representative samples. We are extending previous research by assessing the relationship between a range of variables from both the physical activity and food environments and obesity. Our work features four further elements of uniqueness.

First, our statistical models will incorporate the combined influence of both the PA and food environment. Second, findings will be confirmed by both BMI and waist circumference measurements. Third, we will assess any interactions by education level by posing the question: do more educated individuals have a greater availability of facilities despite living in a deprived area?

Finally, research undertaken in collaboration with Central Queensland University, Australia will begin to bring together associations between the environment and obesity by accounting for individual behaviours such as fast-food consumption and physical activity levels (Figure 1). Similar research is also being conducted by Dr Claire Griffiths and Dr Duncan Radley assessing the links between the environment, individual behaviours and obesity. The development of a novel mobile phone app allows individuals to objectively record their location and the food or physical activity related behaviour. It is hoped that through these more powerful research approaches we will begin to establish the actual relationship between our immediate environment and obesity. In practice, these findings will inform local authorities and other organisations responsible for creating healthy environments on what effect the environment is actual having on obesity and where is best to intervene.

Figure 1 – Research will begin to account for how individual behaviour may influence the relationship between the environment and obesity.

Individual behaviour chart

[1]Astell-Burt T, Feng X, Kolt GS (2014) Greener neighborhoods, slimmer people? Evidence from 246,920 Australians. Int J Obes (Lond) 38: 156-159.
[2]Astell-Burt T, Feng X, Kolt GS (2014) Greener neighborhoods, slimmer people? Evidence from 246,920 Australians. Int J Obes (Lond) 38: 156-159.
[3] Black C, Moon G, Baird J (2014) Dietary inequalities: What is the evidence for the effect of the neighbourhood food environment? Health and Place 13: 131-137.
Ding D, Gebel K (2012) Built environment, physical activity, and obesity: what have we learned from reviewing the literature? Health and Place 18: 100-105.

Matthew Hobbs

Matthew Hobbs is a PhD Candidate at Leeds Beckett University studying the built environment and its relationship with obesity. He is also a Lecturer in Physical Activity, Exercise and Health at Leeds Trinity University.