Fast food, other food choices and body mass index in teenagers in the United Kingdom (ALSPAC): a structural equation modelling approach

Objective: To assess the association between the consumption of fast food (FF) and body mass index (BMI) of teenagers in a large UK birth cohort. Methods: A structural equation modelling (SEM) approach was chosen to allow direct statistical testing of a theoretical model. SEM is a combination of confirmatory factor and path analysis, which allows for the inclusion of latent (unmeasured) variables. This approach was used to build two models: the effect of FF outlet visits and food choices and the effect of FF exposure on consumption and BMI. Results: A total of 3620 participants had data for height and weight from the age 13 clinic and the frequency of FF outlet visits, and so were included in these analyses. This SEM model of food choices showed that increased frequency of eating at FF outlets is positively associated with higher consumption of unhealthy foods (beta=0.29, P<0.001) and negatively associated with the consumption of healthy foods (beta=-1.02, P<0.001). The SEM model of FF exposure and BMI showed that higher exposure to FF increases the frequency of visits to FF outlets (beta=0.61, P<0.001), which is associated with higher body mass index standard deviation score (BMISDS; beta=0.08, P<0.001). Deprivation was the largest contributing variable to the exposure (beta=9.2, P<0.001). Conclusions: The teenagers who ate at FF restaurants consumed more unhealthy foods and were more likely to have higher BMISDS than those teenagers who did not eat frequently at FF restaurants. Teenagers who were exposed to more takeaway foods at home ate more frequently at FF restaurants and eating at FF restaurants was also associated with lower intakes of vegetables and raw fruit in this cohort. International Journal of Obesity (2011) 35, 1325-1330; doi: 10.1038/ijo.2011.120; published online 28 June 2011