Health behaviours as mediating pathways between socioeconomic position and body mass index

Low socioeconomic position is widely reported to associate with high body mass index (BMI). We, however, lack scientific evidence if health behaviours mediate the association between socioeconomic position and BMI.

The aims of the study were to explore associations of education and income with BMI and to study the mediating pathways through health behaviours.

Study population comprised 3,995 Finnish men and women aged 25 to 64 years who participated in a cross-sectional, population-based FINRISK 2002 Study. Participants' height and weight were measured to calculate BMI. Self-administered questionnaire assessed education, household income, leisure time physical activity, sitting behaviour, dietary habits, smoking, and alcohol consumption. Structural equation modelling with latent variables was applied to estimate age-adjusted direct and indirect associations between variables.

Most health behaviours mediated the association between socioeconomic position and BMI. Strongest and most consistent mediators were diet and sitting in men and women, as well as leisure time physical activity in women. Health behaviours clustered strongly with each other.

The strongest indirect associations between socioeconomic position and BMI were mediated through variables related to energy balance, i.e. diet and sedentariness. To reduce the socioeconomic variation in overweight and obesity, the main focus should be on food and sedentary behaviours while also taking into account the gender differences and clustering of unhealthy behaviours.