Independent and combined associations between fast-food outlet exposure and genetic risk for obesity: a population-based, cross-sectional study in the UK.
BMC medicine 2021 ; 19: 49.
PubMed ID : 33588846
Characteristics of the built environment, such as neighbourhood fast-food outlet exposure, are increasingly recognised as risk factors for unhealthy diet and obesity. Obesity also has a genetic component, with common genetic variants explaining a substantial proportion of population-level obesity susceptibility. However, it is not known whether and to what extent associations between fast-food outlet exposure and body weight are modified by genetic predisposition to obesity.
We used data from the Fenland Study, a population-based sample of 12,435 UK adults (mean age 48.6 years). We derived a genetic risk score associated with BMI (BMI-GRS) from 96 BMI-associated single nucleotide polymorphisms. Neighbourhood fast-food exposure was defined as quartiles of counts of outlets around the home address. We used multivariable regression models to estimate the associations of each exposure, independently and in combination, with measured BMI, overweight and obesity, and investigated interactions.
We found independent associations between BMI-GRS and risk of overweight (RR = 1.34, 95% CI 1.23-1.47) and obesity (RR = 1.73, 95% CI 1.55-1.93), and between fast-food outlet exposure and risk of obesity (highest vs lowest quartile RR = 1.58, 95% CI 1.21-2.05). There was no evidence of an interaction of fast-food outlet exposure and genetic risk on BMI (P = 0.09), risk of overweight (P = 0.51), or risk of obesity (P = 0.27). The combination of higher BMI-GRS and highest fast-food outlet exposure was associated with 2.70 (95% CI 1.99-3.66) times greater risk of obesity.
Our study demonstrated independent associations of both genetic obesity risk and neighbourhood fast-food outlet exposure with adiposity. These important drivers of the obesity epidemic have to date been studied in isolation. Neighbourhood fast-food outlet exposure remains a potential target of policy intervention to prevent obesity and promote the public's health.
Some individuals are more likely to develop obesity as a result of their genetic makeup. However, rapidly rising rates of obesity have prompted new questions surrounding the importance of the built environment, aspects of which have changed dramatically in recent decades. In particular, the density and distribution of retail food outlets in our towns and cities. Researchers have demonstrated links between people’s access to fast-food outlets on the high street and their body weight and risk of obesity. This growing body of evidence is helping urban planners to design and redesign neighbourhoods that support healthy food choices.
To date, genetics and environments have been studies in isolation. Researchers have been unable to account for our genes in studies of fast food access and body weight, and have been unable to examine the extent to which impacts of fast food exposure differ according to genetic obesity risk. The theory being that some genes, for example those that have been associated with a preference for high-fat foods, might render those who possess them with a greater susceptibility to the influence of fast food retail.
For the first time, using detailed genetic and environmental data, alongside accurate measurement of body mass index and obesity, for nearly 11,000 adults who took part in the Fenland Study, we have been able to address these gaps in knowledge.
We calculated a genetic risk score for obesity, and counted fast-food outlets within home neighbourhoods. After confirming previously reported relationships between genetic risk for obesity, higher weight and being obese, we found that after taking this into account, those most exposed to fast-food outlets weighed more and were a half more likely to be living with obesity. However those more genetically at risk of obesity were no more susceptible to fast-food outlet exposure, in terms of either body weight outcome. Compared to those least exposed to fast-food outlets and with lower genetic risk, those most exposed to fast-food outlets and at higher genetic risk were nearly three times more likely to be obese.Urban planners might use these findings to justify a continued focus on building healthier towns and cities, in the knowledge that the effects of these changes are unlikely to be different according to population genetics.