Roux-en-Y gastric bypass surgery can fail approximately 20% of the time and may lead to weight loss effects wearing off as the gut grows back receptors.

“it only works about 80 of the time you know my surgeries not a precise science and they're still trying to figure out exactly what nerves you need to cut to have that effect on the body and the other problem with this surgery is that sometimes people grow their guts back the gut is an amazingly resilient organ and it seems that in some cases people start growing new receptors for these fats along the gut and you know the effect can wear off after a while and the Obesity comes back”