The body mass index calculation in the introduction provides doctors with the ability to classify obesity. Anybody with a BMI of over 35 greatly increases their risks of developing co-morbidities (diseases directly linked or caused by being obese). This includes diabetes, arthritis, heart disease and some forms of cancer. Reducing weight by even 5 BMI points significantly reduces these risks.

The ideal BMI for any person is 25, which may be a target out of reach for many obese people but the challenge is to find a treatment that brings a permanent significant reduction in BMI.

Obesity often develops in a "yo-yo" pattern as patients go through non-surgical weight loss programmes losing weight and then regain it after the programme has finished. Studies have shown that for treating morbid obesity (BMI greater than 35) conventional non-surgical weight loss regimes have little chance of success. 

Surgery has been successful over the years and involves altering the anatomy of the stomach and intestine to reduce intake and absorption of food. Results are good in terms of sustained weight loss but some side effects can occur such as persistent diarrhoea, vitamin deficiencies and the surgical alterations breaking down. These procedures have been performed for over 15 years and are mainly performed via a laparotomy (opening the abdomen surgically).

Over the last ten years minimally invasive procedures have been developed

Some centres are starting to look at the possibility of genetic therapies for treating obesity as researchers have found genetic links to obesity in animal models but any trial treatment has yet to be developed.