There is none - by design. In fact, they only follow up on WLS patients for the first year, which is a honeymoon period, when most of the problems have not yet had a chance to become apparent. The interference of these procedures in nutrient absorption doesn't become apparent until they start to show serious signs of nutrient deficiences... more than a year after the procedure. But that doesn't matter from a surgical standpoint, because they're fully recovered from the procedure, the surgeon has released the patient from any further care (washed his hands of the patient), and therefore has absolutely no responsibility for anything that happens after that.

I can understand this happening back when WLS was in it's infancy, and it looked like the patients were doing well, and had stabilized after a year, so why not release them from follow up care? But after so many years, and using so many different WLS procedures which result in the same types of problems cropping up later, it should be so obvious that none of them continue to do well after that first year, and it's not just because the patient has become complacent, failed to adequately deal with the emotional aspects of why they gained so much weight to begin with, or returned to old ways of eating (even though those things do often happen) - it should be so obvious that the physical problems occur because something about WLS is only a temporary bandaid (which is mostly the bypassing of the duodenum and the necessary hormone triggers that are switched off permanently - saw a video the other day by Dr Mike Eades about the incretin/GIP/GLP interactions that explains it in more detail than I fully understood), and therefore not a permanent fix for the problems that existed before their WLS. Because of that, and the very way these primarily irreversible procedures are constructed, their health is eventually far worse than before.

The only "logic" I can see in continuing to do these procedures, and coming up with less invasive/sometimes somewhat reversible procedures (instead of changing the diet that caused the problem to begin with) is that they don't believe people who have spent their lives eating a certain way will ever willingly change their way of eating without a "tool" that makes them even more miserable if they eat or drink even 1 more swallow than they're allowed. Of course if the only alternative they're offering to an unlimited SAD diet is a low fat, low cal diet, it's no wonder they can't stop eating the very things that are triggering their out of control hunger. Even if the medical establishment ever accepts LC as the best way to bring all the problems under control, there are still going to be those who won't give up their bread and potatoes, can't imagine their life without cereals, fries, and donuts, and refuse to even try.