Associations between exposure to takeaway food outlets, takeaway food consumption, and body weight in Cambridgeshire, UK: population based, cross sectional study
- “Associations between exposure to takeaway food outlets, takeaway food consumption, and body weight in Cambridgeshire, UK: population based, cross sectional study” by Thomas Burgoine and colleagues (BMJ 2014;348:g1464, doi:10.1136/bmj.g1464).
Objectives To examine the association between environmental exposure to takeaway food outlets, takeaway food consumption, and body weight, while accounting for home, work place, and commuting route environments.
Design Population based, cross sectional study, using data on individual participants’ diet and weight, and objective metrics of food environment exposure.
Participants Working adults participating in the Fenland Study, Cambridgeshire, UK (n=5442, aged 29-62 years), who provided home and work addresses and commuting preferences. Takeaway food outlet exposure was derived using data from local authorities for individual environmental domains (at home, at work, and along commuting routes (the shortest route between home and work)), and for exposure in all three domains combined. Exposure was divided into quarters (Q); Q1 being the least exposed and Q4 being the most exposed.
Main outcome measures Self reported consumption of takeaway type food (g/day; pizza, burgers, fried foods, and chips) using food frequency questionnaires, measured body mass index, and cut-offs for body mass index as defined by the World Health Organization.
Results In multiple linear regression models, exposure to takeaway food outlets was positively associated with consumption of takeaway food. Among domains at home, at work, and along commuting routes, associations were strongest in work environments (Q4 v Q1; β coefficient=5.3 g/day, 95% confidence interval 1.6 to 8.7; P<0.05), with evidence of a dose-response effect. Associations between exposure in all three domains combined and consumption were greater in magnitude across quarters of exposure (Q4 v Q1; 5.7 g/day, 2.6 to 8.8; P<0.001), with evidence of a dose-response effect. Combined exposure was especially strongly associated with increased body mass index (Q4 v Q1; body mass index 1.21, 0.68 to 1.74; P<0.001) and odds of obesity (Q4 v Q1; odds ratio 1.80, 1.28 to 2.53; P<0.05). There was no evidence of effect modification by sex.
Conclusions Exposure to takeaway food outlets in home, work, and commuting environments combined was associated with marginally higher consumption of takeaway food, greater body mass index, and greater odds of obesity. Government strategies to promote healthier diets through planning restrictions for takeaway food could be most effective if focused around the workplace.
Why do the study?
Worldwide, obesity has nearly doubled since 1980, and more than 10% of the world’s adult population is currently obese. Being overweight is now perceived as the norm. Although obesity is preventable, strategies to tackle it are difficult to implement. The World Health Organization recommends that governmental policy in sectors such as health, agriculture, and education should be established to enforce local communities to play a role in helping to shape people’s choices, and therein reduce the burden of obesity. In the United Kingdom, such policies are already implemented, with the east London borough of Waltham Forest being the first to reject applications from those who wanted to open up takeaway food outlets within 400 yards of any school, youth club, or park.
Overconsumption of takeaway foods has been linked to low diet quality, weight gain, and insulin resistance. In the United Kingdom, consumption of food prepared away from home has increased by 29% over the past decade. Alongside this, there has been a 79% increase in the number of takeaway food outlets over the past 20 years. Whether or not the two are linked is controversial, with some studies reporting a positive association and others not. This study’s authors hypothesised that these discordant results may be accounted for by differences in researchers’ definitions of neighbourhood, food outlet type, and the assessment of dietary intake. Furthermore, until now little attention has been paid to a participant’s “activity space,” which, in addition to their home and surrounding area, consists of their commuting route to work and their workspace itself.
What did the authors do?
The authors aimed to examine the health effects of living in an “obesogenic activity space.” They suggest that such areas may facilitate the overconsumption of energy dense, nutrient poor foods, and have increased levels of obesity. They designed a large cross sectional study of working adults living around Cambridgeshire that sought an association between density of takeaway food outlets and self reported consumption of takeaway foods and body mass index.
Cross sectional studies are a type of descriptive study used to look at one or more variables within a given population. Data are collected from participants at one time point only. As participants are not followed up over a defined period, cross sectional studies only provide a snapshot of frequency of disease (prevalence) or health characteristic in a population. They are often used to determine associations between variables. This differs from longitudinal and experimental studies, which follow participants over time and, if a randomised intervention is tested, can tackle causality.
Participants in this study were already enrolled in a Medical Research Council sponsored prospective epidemiology cohort study: the Fenland study. Since 2005, adults aged 29-62 participating in the Fenland study attended a single three hour appointment and completed questionnaires related to general lifestyle, medical history, and food frequency. In addition, body mass index and energy expenditure from physical activity were calculated.
All working adult participants in the Fenland study were eligible for inclusion in this current study. Following exclusions of people who had incomplete data for work addresses, lived or worked far outside Cambridgeshire, and worked from home, data for 5594 participants were used for analysis.
Participants’ home and work activity spaces were defined as being within a one mile radius of their respective addresses and were accurately mapped using a geographical information system. Using commuting travel mode (car versus cycling or walking) and frequency as reported by each participant, commuting routes were modelled according to the shortest distance along streets between work and home addresses.
The authors then verified the numbers of takeaway food outlets in each of the participants’ home, work, or commute areas using local council data. Exposure to a takeaway outlet was categorised into quarters—where the lowest quarter (first quarter) represented the 25% of the population studied who were least exposed to takeaway food outlets, and the highest quarter (fourth quarter) represented the 25% of the population who were most exposed to takeaway food outlets. The authors excluded workplace canteens and restaurants that did not sell directly to the public.
Based on responses to the food frequency questionnaires, the authors then estimated the amount of takeaway food (defined as burgers, pizzas, chips, and fried food) eaten (g/day). Regression models were used to estimate associations between density of takeaway outlets in home, work, and commuting activity spaces and body mass index, as well as self reported energy consumption. Covariates, such as age, sex, socioeconomic status, car ownership, and total energy intake were included in the models to ensure that potential bias from confounding factors was accounted for among participants.
What did the study find?
On average, the population sample was exposed to 9.3 takeaway food outlets at home, 13.8 at work, and 9.3 along commuting routes. Participants were exposed to the availability of 48% more takeaway food outlets at work than at home.
Self reported consumption
At home, participants most exposed to takeaway food outlets (fourth quarter) consumed 4.9 g/day (95% confidence interval 1.5 to 8.3, P<0.05) more than those who were least exposed (first quarter, fig 1 1 ). At work, participants in the fourth quarter consumed an additional 5.3 g/day (1.6 to 8.7, P<0.05) compared with those in the first quarter. A dose-response association between increasing exposure and consumption was not seen, nor was any significant association seen for exposure along commuting routes.
Body mass index
Similar results were seen for the other outcomes. At home and along commuting routes, participants in the fourth quarter had a higher mean body mass index than those in the first quarter, with a difference of 0.97 and 0.65, respectively (fig 2 2 ). At work, the most exposed group (fourth quarter) had a higher mean body mass index compared with the least exposed group (first quarter): difference of 0.92, P<0.05.
Participants in the fourth quarter in their home spaces were more than twice as likely to be obese (odds ratio 2.15, 95% confidence interval 1.50 to 3.10) compared with those in the first quarter. Along commuting routes, participants in the most exposed quarter showed 38% greater odds of being obese than those in the least exposed quarter (1.38, 1.01 to 1.88). At work, the most exposed group showed a 47% greater odds of being obese compared with the least exposed group (1.47, 1.03 to 2.10).
Results regarding dose-response relations between increased exposure to takeaway food outlets and body mass index and risk of being obese can be obtained from the original study.
What are the strengths and limitations of this study?
This is one of the first studies to look at home, work, and commuting neighbourhoods when analysing risk of exposure to takeaway food and adverse health outcomes. Previously conducted research focused on residential neighbourhoods only. By looking at all three environments, more exposure domains were studied and an increased number of associations could be determined.
Recruitment for this study was carried out by accessing general practice lists in Cambridgeshire, United Kingdom. This is an ideal way to recruit participants as it makes the population studied generalisable and reduces selection bias, where some people are not offered equal opportunity to partake in the study.
There are some notable limitations. Only working, relatively affluent adults were included in the study. Although this may reflect the population in Cambridgeshire, it is unlikely that these data are applicable to more impoverished areas or to those patients with high levels of unemployment.
As with any cross sectional study, it is difficult to determine if the outcome definitively followed the exposure or vice versa—for example, did people exposed to a takeaway food outlet alter their consumption of takeaway food before or after the outlet opened? This type of question, addressing causality, can never be answered from a cross sectional study, which is why only association can be established.
The authors rightly note that data for this study were collected from 2005, but data regarding the mapping of takeaway outlets used were collected from 2011. Since the number of takeaway outlets has increased from 2005 to post-2011, this study may overestimate the amount of exposure by some participants.
Lastly, the study excluded food outlets that were not open to the public but may still be a source for “takeaway food” such as workplace canteens, which may have underestimated exposure.
What does this study mean?
Those who have increased exposure to takeaway food outlets in their home, work, and commuting environments are associated with an increased likelihood of consuming takeaway foods, having a higher body mass index, and being obese.
Governments and legislators are beginning to use data from studies like this to implement local policies that encourage healthy eating and lifestyle. For example, New York city in the United States has recently placed restrictions on selling large sugary drinks, and the city of Austin, Texas has banned takeaway food within close distances to schools—both in an effort to create “healthy food zones.” 
Much is being considered for preventing obesity in children and adolescents, but adults continue to remain susceptible to poor diet and obesity, particularly in the context of new takeaway food outlets opening up in home and work neighbourhoods. Regulation of such local businesses, particularly near work neighbourhoods, may be the next step in helping to promote healthier lifestyles.
Eyespy, p 44
1Whipps Cross Hospital, London
Correspondence to: email@example.com
Competing interests: None declared.
Provenance and peer review: Commissioned; not externally peer reviewed.
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Cite this as: Student BMJ 2014;22:g2857