Hi ris3r,My son lifts weights and was into taking lots of protein shakes until he was warned off the by his doctor. Turns out his kidney function was suffering. Large amounts of protein stresses them. He takes one for breakfast made with lots of healthy things, but doesn't pump them down like he used to.
I'm sure in moderation they would be fine. I think if you want them to help with healthy weight gain, they must be accompanied by a little strengthening exercise. As Alcie said, call your surgeon's office and get the specifics of what he meant by "heavy weights", and what your restrictions/timing are.
I have no doubt that you'll get your strength back, but listen to your body. If it hurts, back off.
Patience...you'll be back to your old self soon!
Hang in there...
Denise