This article describes the "incretin effect" which occurs after bariatric surgery such as gastric sleeve and gastric bypass.
This also explains why other procedures such as the balloon and lap band are not as effective because they do not alter the incretin hormones mentioned in this article.
Obesity is being recognised by the College of GPs as a chronic medical condition that requires ongoing management. Stigmatisation regarding obesity needs to be diminished. Governments need to start recognising obesity as a true, medical problem and fund effective treatments such as bariatric surgery.