Food prepared out-of-home is typically energy-dense and nutrient-poor. More frequent consumption of this food is associated with poorer overall dietary patterns and obesity. Previous research has tended to focus on access to food prepared out-of-home in the physical food environment, which is often greatest in more deprived areas. However, this food can now also be accessed through online food delivery services. Although online food delivery services are globally established, there is limited public health knowledge about the prevalence of their use and factors influencing this, the sociodemographic characteristics of customers, and the extent to which the opportunity to use them is socioeconomically patterned. The aim of my thesis was to help better understand the use of online food delivery services to access food prepared out-of-home.

First, I analysed survey data collected in 2018 to identify the prevalence of online food delivery service use and the sociodemographic characteristics of adult customers across Australia, Canada, Mexico, the United Kingdom, and the United States of America. From 19,378 respondents, around one in six had used an online food delivery service in the past week. Respondents who were male, younger, more highly educated, living with children and those who identified with an ethnic minority had greater odds of online food delivery service use. These patterns were similar in each country but the strength of associations varied. Notably, respondents with a high versus low level of education had greater odds of online food delivery service use in all countries except the United Kingdom.

Second, I conducted telephone interviews with 22 adults living in England who were frequent online food delivery service customers. Participants reported that they could access a higher number of food outlets and a broader range of cuisines through online food delivery services compared with the physical food environment. Additionally, these services allowed participants to access exclusive price-promotions and use streamlined purchasing processes, which were seen as unique advantages. Participants reported that they believed the food available through online food delivery services was mostly unhealthy. Nevertheless, this food met their expectations about takeaway food. Despite reported drawbacks of online food delivery services, which included over-convenience and, paradoxically, access to unhealthy food, participants reported no intention to discontinue use because it was normal to purchase food prepared out-of-home in this manner.

Informed by existing evidence and my qualitative research, I investigated associations between access to food prepared out-of-home through online food delivery services and online food delivery service use, and body weight. In my individual-level data-linkage study of 3067 adults living in Great Britain, the number of food outlets accessible online was positively associated with online food delivery service use in the past week. However, it was not associated with body weight. Despite the perspective of frequent customers, the number of cuisine types accessible online was not associated with online food delivery service use.

Finally, I examined access to food prepared out-of-home through online food delivery services in England and variation according to area-level socioeconomic position. In a cross-sectional study, I found that the number of food outlets accessible online was highest in the most deprived areas of England in November 2019. I followed this with a repeat-cross sectional study that assessed changes in the number of food outlets accessible online over time, within the context of the Coronavirus Disease 2019 (COVID-19) pandemic. I found that it was only in the most deprived areas of England that the number of food outlets accessible online in March 2022 surpassed the number from November 2019. Taken together, these findings indicate that online access to food prepared out-of-home in England is socioeconomically patterned, and that inequalities therein widened over time.

The findings from my thesis help better understand multiple aspects of online food delivery service use. The number of food outlets accessible online emerged as being particularly important. A higher number was positively associated with online food delivery service use, which suggests it can influence food purchasing practices. Indeed, this was supported by the views of frequent online food delivery service customers in my qualitative research. Additionally, the number of food outlets accessible online was highest in the most deprived areas of England in November 2019, and increasingly so over time compared with less deprived areas. Thus, the opportunity for online food delivery service use is unequal across the socioeconomic spectrum in England. Future research should seek to understand how food purchased through online food delivery services contributes to overall dietary patterns and health, and the need for public health intervention.