A novel approach to latent class modelling: identifying the various types of body mass index individuals

Given the increasing prevalence of adult obesity, furthering understanding of the determinants of measures such as Body Mass Index (BMI) remains high on the policy agenda. We contribute to existing literature on modelling BMI by proposing an extension to latent class modelling, which serves to unveil a more detailed picture of the determinants of BMI. Interest here lies in latent class analysis with: a regression model and predictor variables explaining class membership; a regression model and predictor variables explaining the outcome variable within BMI classes; and instances where the BMI classes are naturally ordered and labelled by expected values within class. A simple and generic way of parameterising both the class probabilities and the statistical representation of behaviours within each class is proposed, that simultaneously preserves the ranking according to class-specific expected values and yields a parsimonious representation of the class probabilities. Based on a wide range of metrics, the newly proposed approach is found to dominate the prevailing one; and moreover, results are often quite different across the two.