The effects of takeaway (fast) food consumption on UK adolescent’s diet quality and BMI

Many existing NCDs have emerged not only due to the increasing rates of obesity and overweight among children, but also because of children’s unhealthy diets. Adolescence may be one of the best times to tackle health problems and alert young people to the need to improve their dietary behaviour. Dietary habits are reportedly shaped during adolescence, and the habits formed in this period can potentially last into adulthood. Examining the intakes of individual nutrients or food items is not enough to assess overall diet quality, as both the quality and variety of the whole diet must be considered. The surrounding food environment, particularly takeaway food outlets, is also believed to affect an individual’s diet quality and obesity risk. However, few researchers have explored the associations between takeaway consumption, types of school lunch and overall diet quality among adolescents. Moreover, worldwide, there are no standardised measures used to calculate the density and proximity of food outlets around homes, schools, work or any other facilities. In addition, few studies have explored the longitudinal associations between the takeaway food environment and secondary school adolescents’ BMI and body fatness. This thesis first investigated the associations between takeaways and meals-out consumption (at and outside the home) and overall diet quality in UK adolescents from the National Diet and Nutrition Survey (NDNS) years’ 1–6 data. Frequent consumption of takeaway meals and meals out have been found to be negatively associated with the diet quality of British adolescents aged 11–18 years. Subsequently, I explored the associations between the types of lunch consumed on a school day and UK adolescents’ overall diet quality, also using also the NDNS years’ 1–8 data. Students purchasing food from shops or cafes were found to have statistically lower overall diet quality scores compared with other sources of lunches, including hot and cold school meals and packed lunches brought from home. Next, I investigated the differences in using different methods for evaluating the school food environment using Avon Longitudinal Study of Parents and Children (ALSPAC) data. I located both schools and hot food takeaways (HFTs) using ArcGIS software. Statistical distinctions were observed between straight-line and road network density and the proximity of HFTs. Moreover, Lin’s concordance correlation coefficient test showed that both methods were in a poor-to-moderate strength of agreement. I also used the Hansen Index, whereby both the number and proximity of the outlets were considered. Finally, I investigated the longitudinal associations between availability, proximity and accessibility of HFTs and Body Mass Index (BMI), as well as the body fatness of school adolescents. The participants were included from the ALSPAC study and visited the clinic five times during the study period at age 11, 12, 13, 15 and 17 years. Consistent with the previous findings, the overall results regarding the associations between availability, proximity or accessibility of HFTs and BMI and body fat percentage of school adolescents showed null/negative associations. This thesis highlights the importance of being a takeaway consumer on overall diet quality, especially during childhood. These findings are likely to be useful for informing future governmental policies to improve the dietary behaviour and health status of young people in the UK. This work also helped in highlighting the importance of consistent methods to be used to measure the food environment, especially around schools which, therefore, may lead to more effective policies. Finally, the findings also show that focusing solely on HFTs may not support the hypothesis that limiting the number of food outlets around schools would reduce the risk of being obese or having a higher body fat percentage. In this age group, more comprehensive measures may be needed to improve the food environment near schools.