Smartphone-based dietary assessment of food away from home and the risk of non-communicable diseases among young working adults in Johannesburg, South Africa

Background: The rising consumption of food away from home (FAFH) among young working adults is a growing public health concern, particularly due to its association with non-communicable diseases (NCDs). Objective: This study employed ‘FoodLog’, a validated smartphone-based dietary tracking application, to investigate the determinants of FAFH consumption and its relationship with NCD risk among young adults. Design: Case-control study. Setting: Johannesburg, South Africa. Subjects: The analysis included 442 employed adults aged 25–45 years. Cases (146) were defined as individuals with self-reported NCDs, while controls (296) had no NCDs. Outcome measures: The primary outcome measures were the identification of determinants of FAFH consumption and the assessment of its association with NCD risk, using multivariate logistic regression models. Results: Multivariate analysis revealed that 33% of participants consumed FAFH in the week before the survey. Significant associations were found between FAFH consumption and female gender (AOR = 1.52, CI: 1.01–2.30), higher education (AOR = 2.05, CI: 1.16–3.61), physical inactivity (AOR = 2.44, CI: 1.56–3.79), and low vegetable intake (AOR = 1.33, CI: 1.09–1.57). Additionally, NCDs were more prevalent among individuals reporting alcohol use, non-vegetarian diets, and frequent FAFH consumption. FAFH consumers were 1.12 times more likely to report NCDs than non-consumers (AOR = 1.12, 95% CI: 1.01–1.61). Conclusion: These findings underscore the utility of mobile dietary assessment tools in capturing nuanced eating behaviours and highlight the need for targeted interventions addressing both individual choices and the urban food environment to reduce NCD risk.