Identity is a determinant of health-promoting behaviours such as physical activity and health-compromising behaviours such as smoking. This scoping review provides a comprehensive synthesis and comparison of the relationship between physical activity- and smoking-related identity and behaviour, and how these identities are defined and measured. Study participants’ personal, physical activity-related and smoking-related characteristics were considered if data were available. The review focuses on people aged 45 and above.

A search across 9 databases yielded 5801 unique publications. Ensuing careful screening, 268 peer-reviewed empirical studies met eligibility criteria, of which 45 concerned participants of 45+ age. Experts in the field contributed to validating and structuring the narrative.

Findings revealed the existence of an intricate, enduring direct and indirect relationship between identity and behaviour for physical activity and smoking. Numerous similarities and differences in this relationship, as well as in identity-related terminology and measurement tools used, were identified. In essence, endorsing an identity related to physical activity and smoking abstinence was found to be important for becoming physically active and quitting smoking successfully, respectively. Identity processes, encompassing identity formation, maintenance, change and loss, were detected as applicable to both physical activity and smoking, although differences were observed between the two behaviours. Characteristics such as gender, age and behavioural history emerged as relevant in shaping smoking-related and physical activity-related identities.

Despite variances, findings suggest that the relationship between identity and behaviour, including associated processes, may not fundamentally differ between health-promoting and health-compromising behaviours. Avenues for future research, including exploring causality between identity and behaviour, are proposed.