Best guide is the BMI

>40, or >35 with comorbid conditions is an indication of bariatric surgery.

Also, patients in whom medical therapy, lifestyle therapy has failed/ with noncompliance; bariatric surgery is indicated

Thanks for your input Dr.Shah, but my question was based on: what exactly is "medical therapy, lifestyle therapy has failed" ?? What is the time duration that medical therapy should be tried? How to define 'non-responders' ? 

Rangarajan,

Unfortunately, the answer is not straight forward. It requires clinical understanding by physicians and is based on recommendations of several organization (see link below).  Most of the decisions are individually based. Some medical insurance companies set guidelines for reimbursement based on aggregates. The length of time failing at lifestyle/medical change (diet and exercise) and medicines to stimulate thyroid or reduce appetite to reverse obesity varies from 6 months of documented diets to one year. When co-morbidities such as diabetes and hypertension are considered, the judgement of a physician is often enough. Uncontrollable diabetes is also an individual consideration by a physician. Usually hemoglobin A1c levels are 8.5 or over and do not respond to treatment.

https://asmbs.org/resources/bariatric-surgery-guidelines-and-recommendations

Dear Dr.Vaccaro,

Many thanks for your input. Like you mentioned, unfortunately it seems there are no clear guidelines. I started this discussion because if there are no guidelines, surgeons may be biased toward surgery in many cases, and physicians may be biased against surgery

I agree with what has been stated. However, there are some trials comparing bariatric surgery vs optimal medical treatment for type 2 diabetes and results have been consistently better with surgery. Therefore, if the patient is a good candidate (and patient selection is critical) and has failed medical therapy and lifestyle intervention, I think that surgery should be offered as an option. 

Thanks Dr.Chen-Ku.

My query was just this: what exactly is  "failed medical therapy and lifestyle intervention" and "patient selection" ??

For morbidly obese or obese with comorbidities, best improvements including type 2 diabetes and other risk factors, gastric bypass surgeries have been more effective. There is swedish obese study on 10-20 year follow up as well our publications (Bigornia et al) on 5 year follow up indicate similar results.