Losing tons of hair but not the weight!

Sorry, always difficult to answer without knowing the details.

Can't see how it could be the band at four years post-op. 

Why do you think your weight didn't come off?

Check your meds they may be the culprit to the hair loss.

Have you had your iron checked?  And, by that, I mean not just your ferritin but the whole nine yards.  Some doctors only order the most obvious iron test but not the others.  There are more iron tests that can done besides that one.  Iron deficiency anemia will cause hair loss. 

Also is there any other major stress going on in your life.  All major stress can cause hair to fall out and just good old fashion genes can be the problem.