Background:

The recent epidemiology and biology demonstrated the horizontal (i.e. via social network) and vertical (i.e. inheritable to children) infection of obesity. Vertical transmission of obesity can have a substantial impact on policy making of public health and demography.  Apart from that, the relationship between the obesity epidemic and its impact on demography is not cleared so far. This study aims to construct the obesity epidemic model accounting for vertical infection of obesity and investigate the impact of obesity epidemic on the demography.

Methodology/Principal Findings:

Firstly, we constructed the obesity epidemic model accounting for vertical infection of obesity in ordinary differential equations. Subsequently, we analyzed the model, especially defining the reproduction number of total population (i.e. the mean number of children that a typical female produce in her life time) and calculating the future converged prevalence of obesity. Secondary, we investigated the impact of vertical infection of obesity on the prevalence of obesity and demography with varying the obesity related parameters which are not quantified so far. Our findings suggest that the population growth in the US is maintained by the relative fertility rate of the obese in the realistic parameter settings, and the relative fertility rate of obesity have positive and negative impact on the future converged prevalence of obesity depending on the relative death rate of obesity.

Conclusions:

In this study, we could construct the obesity epidemic model account for vertical infection of obesity. Considering our successful contribution to reveal the importance of vertical transmission of obesity on demography, further studies are required (1) to quantify the parameters that is not cleared so far and (2) to elucidate the detail mechanism of the vertical transmission of obesity for more valid obesity epidemic modelling and precise comprehension of the current situation of obesity epidemic in the US.