According to IFSO / International Federation for Surgery of Morbid Obеsity/ there are a number of widely accepted criteria which make a patient suitable for Bariatric weight loss surgery:

Weight greater than 45kg above the ideal body weight for sex, and height.

BMI > 40 by itself or >35 if there is an associated obesity illness , such as diabetes or sleep apnoea

Reasonable attempts at other weight loss techniques

Age 18-65

Obesity related health problems

No psychiatric or drug dependency problems

A capacity to understand the risks and commitment associated with the surgery.

Pregnancy not anticipated in the first two years following surgery

There is considerable flexibility in these guidelines. Patients as young as 12 have been offered surgery. Sometimes a lower BMI between 30-35 is accepted if comorbidities exist.