Obesity as defined by a body mass index (BMI) greater than 30kg/m² i.e. weight in kilograms divided by height in metres squared, is a worldwide problem. The population prevalence in the UK is approaching 25% and that in the United States approaches 35%. By 2010, the UK prevalence is predicted to reach 33%. The health consequences of obesity are extensive and include hypertension, diabetes, heart disease, arthritis and cancer. Being obese shortens life span. Besides the above well documented deleterious effects on systemic function, obesity also causes liver disease.