BACKGROUND: Young women spend 50 min daily on social media (SM); thus, SM platforms are promising for health interventions. This study tested the feasibility and preliminary efficacy of the co-designed SM intervention the Daily Health Coach (DHC). The DHC is a 3-month healthy lifestyles intervention programme, targeting eating, physical activity, and social wellbeing behaviours in women aged 18-24, via the dissemination of health and nutrition content on social media platform Instagram. METHODS: The programme was tested using an assessor-blinded, two-arm pilot randomised controlled trial with 46 participants over 12 weeks. Engagement was assessed via SM metrics; acceptability via post-programme questionnaires; and feasibility included retention, randomisation, recruitment, and data collection. Secondary outcomes-dietary quality, physical activity, social influence, disordered eating behaviours, body image, and digital health literacy-were assessed using validated surveys. Analyses included -tests, chi-squared tests, and linear mixed models. The treatment effects were estimated by testing mean score differences from baseline to 3 months for intention-to-treat populations. RESULTS: The DHC scored 83.6% for programme satisfaction. Over time, a significant decrease in body image disturbance was observed ( = 0.013). A significant group-by-time interaction for digital health literacy ( = 0.002) indicated increased ability to discern evidence-based nutrition information ( = 0.006). The waitlist control group showed increased social influence compared to the intervention group ( = 0.034). No other significant changes were observed. CONCLUSION: The DHC is a feasible and acceptable method for disseminating nutrition information. Larger studies are needed to determine efficacy.