Communication with young adults about healthy lifestyle behaviours needs to result in improvements in dietary choices to impact the prevalence of diet-related diseases. This paper presents the health beliefs, behaviours, and communication practices in young Australian adults (n = 2019) by their pre-defined psycho-behavioural characteristics: Lifestyle Mavens, Health-Conscious, Aspirational Healthy Eaters, Balanced-All Rounders, Contemplating Another Day, or Blissfully Unconcerned. The Lifestyle Mavens and Health-Conscious groups were more likely to actively seek out health information on social media (p < 0.05). Lifestyle Mavens were the most likely to engage with health and food content on social media, whereas the Blissfully Unconcerned were the least likely to engage (p < 0.05). Lifestyle Mavens are more likely to report creating food and health-related content for social media, whereas Aspirational Healthy Eaters are more likely to report searching for food and health-related content online, but are less likely to share or create content. Contemplating Another Day are more likely to report interactions with commercial content. This paper defines how psycho-behavioural segments communicate about health, where they look for information, how they may prefer to receive health messages, and when they are most receptive to messages. By applying existing robust market segmentation techniques, this paper provides nuanced information that challenges the assumption that online social media health information is preferred by all young adults.