Obesity in single gene disorders.

In the 1980s, the heritability of obesity has been calculated to be around 0.80, implying a significant genetic origin and sparking a worldwide "gold-rush" for causative genes. Since the discovery of leptin and the body weight homeostasis pathway it regulates, we have come to a greater understanding of the factors that now control it. Nevertheless, we are still some way off reaching the goal of effectively managing the consequences of dysregulation: obesity, a disease-related state that threatens the well-being of mankind. An unprecedented plethora of data has informed our understanding of obesogenic processes; this chapter examines the evidence, focusing on the substantial role of monogenic diseases.