Genes and Gene–Environment Interactions in the Pathogenesis of Obesity and the Metabolic Syndrome

In recent years, the prevalence of obesity has risen sharply, becoming a major public health problem, especially in western countries. According to the World Health Organization (http://www.who.int), an estimated 1 billion adults are overweight (body mass index > 25 kg/m2), and 300 million of these are considered clinically obese (body mass index > 30 kg/m2). In part as a result of the rising prevalence of obesity, the incidence of the metabolic syndrome and type 2 diabetes are also reaching the levels of an epidemic. Although our genetic make-up has not changed significantly over the last 50 years, our diet and lifestyle have. This has unveiled how genetic predisposition can affect our response to environmental factors such as nutrition and exercise. In the present chapter we discuss how our genes, alone and in combination with the environment, can give rise to obesity, the metabolic syndrome and diabetes.