The prevalence of obesity among adults, and in particular extreme obesity, has risen rapidly over previous decades. Current levels of extreme obesity (BMI ≥40 kg/m2) in the US have increased 70% over the last decade between 2000 and 2010, with the prevalence rate reaching 6.6%, whilst current UK prevalence rates of extreme obesity are 3% for females and 2% for males. Indeed, recent estimates predict the rate of extreme obesity to reach 5% in the UK by 2033 and 9% in the US by 2030. The physical co-morbidities of extreme obesity are well documented and research suggests that there are also substantial negative impacts of adiposity on depression, anxiety and reduced quality of life.