Disease severity and staging of obesity: a rational approach to patient selection.

The increasing prevalence of obesity places ever-increasing cost demands on healthcare systems. One million individuals are eligible for bariatric surgery in the UK, and yet less than 6000 bariatric procedures are performed annually. Bariatric surgery reverses or improves almost all the medical and psychosocial co-morbidities associated with obesity. Although the BMI is a simple method to estimate adiposity at a population level, it is relatively inaccurate within an individual and provides little-to-no indication of overall health status or disease severity. Staging systems overcome the inherent limitations of BMI and allow highly informed decision-making for an individual. At a societal level, this helps to identify those most likely to gain and maximise economic benefit. This review summarises the co-morbidities associated with obesity and the evidence for their improvement following surgery. The rationale for new staging criteria and appropriate patient selection are discussed.