Infectious and Environmental Influences on the Obesity Epidemic

Over the last two decades, the prevalence of obesity has increased rapidly. While it is intuitively appealing to believe that the causes of obesity are manifestly related to excess dietary intake, combined with a reduced expenditure of energy via a decrease in physical activity, it is also been noted that the evidence for these as the sole causes of the obesity epidemic is incomplete. This has led to the search for other causes of obesity, particularly those which stem from the environment we live in. This review will explore two putative causes of obesity: infections and environmental pollutants. It will focus on the key human infection associated with obesity—human adenovirus 36 (Ad36) and will discuss several environmental pollutants which have been postulated to be involved in the development of obesity: bisphenol A, phthalates and persistent organic pollutants. For each of these, the epidemiology and biological mechanisms underpinning the association of these agents with obesity will be reviewed.