MC 6460
Speaker
John
Lang, PhD
Candidate
Department
of
Applied
Mathematics,
University
of
Waterloo
Title
Modelling the Dynamics of the Body Mass Index (BMI) at the Individual and Population Levels: Evidence for the social spread of obesity
Abstract
The worldwide prevalence of obesity has nearly doubled in the past 35 years, with significant economic, social, and public health consequences. Despite the significant research on the obesity epidemic, however, there is currently no quantitative mechanistic model capable of simultaneously explaining the dynamics of individuals' body mass index (BMI - a standard measure of relative body weight) and the dynamics of the distribution of BMIs in the overall population. A full understanding of individuals' BMI dynamics, their implications for the dynamics of the population-level distribution of BMIs, and how these dynamics have changed over time, has important implications for public health intervention policies. We develop a quantitative mathematical model for the dynamics of individuals' BMI with implications at the population level. At the population level our model is better able to fit empirical BMI distributions than two other distribution functions commonly used to fit right-skewed data, i.e. the log-normal and skew-normal distributions, and provides a mechanistic explanation for the right-skewness observed in empirical BMI distributions. At the individual-level our model is able to reproduce both the average and standard deviation in the year-over-year change in individuals' BMI. At both the population and individual levels our model provides evidence in support of the hypothesis that social factors play a role in the dynamics of individuals' BMI.