Purpose This paper aims to determine the impact of online community participation on attitudes and product-related behaviour in the health and fitness sector. Design/methodology/approach Survey data are collected from 221 users of the social medium Instagram, members of the self-proclaimed health and fitness community (#fitfam). Data are analysed with structural equation modelling. Findings The study shows that online community identification and engagement significantly increase health environment sensitivity, resulting in heightened engagement in physical fitness and healthy product choices. Social implications Given the difficulty to remain engaged in pro-health behaviour and the growing impact of social media on young adults’ lives, these findings are encouraging. They show that online health and fitness communities provide a supportive environment in which consumers can identify and freely engage and a fertile ground to the development of health sensitivity and product-related behaviour. Originality/value The study advances knowledge on the role of social media and online communities in promoting health and fitness product behaviours and attitudes.