The Impact of Adolescents’ Food Purchasing on Overall Dietary Quality Differs by Socioeconomic Status

During adolescence, many young people commence making more independent food purchases. Subsequently, these independent food choices will increasingly contribute to their overall diet quality; little is known, however, about this relationship. This study aimed to (1) understand the role adolescents' independent food purchases play in their overall diet quality and (2) explore if these relationships vary according to socioeconomic status (SES). A one-week observational study was conducted with 108 adolescents, aged 11–18 years, from Hampshire, UK. Participants completed a demographic questionnaire and a validated 20-item Food Frequency Questionnaire, which assessed diet quality. Participants also used a mobile phone app to record their food purchases. The healthfulness of food purchases was assessed against UK healthy eating guidelines. Linear regression models were used to investigate associations between the healthfulness of food purchases and diet quality. An interaction term was used to determine the modification effect of SES. During the study week, 583 food/drink items were purchased on 273 food-purchasing occasions by 80 participants. The majority of purchases (n = 359, 62%) were coded as 'not adhering' to the UK Eatwell Guide, 30% were coded as 'adhering' and 8% were coded as uncategorised foods. No notable differences were observed in the healthfulness of food purchases according to age, gender, ethnicity or SES. Healthier food purchasing was associated with better diet quality (β 0.52, (95% CI 0.06, 0.99) p = 0.03); the results were attenuated after adjustment (β 0.41, (95% CI −0.08, 0.91) p = 0.10). Interaction analysis showed that the healthfulness of purchases was more strongly associated with diet quality among young people of lower SES (p = 0.06). Discussion: The majority of purchases made by adolescents were categorised as 'not adhering' to healthy eating guidelines. For adolescents experiencing disadvantage, these food choices had a more detrimental impact on their overall diet. We speculate this is because independent food choices represent a greater proportion of the foods consumed by these adolescents compared to those who are less disadvantaged. Finding ways to support more healthful independent food choices among adolescents, particularly those from disadvantaged backgrounds, is important to improve dietary quality and reduce inequalities.