Weight loss is a math problem.
Structural integrity is an engineering problem. The new drugs solve the first. They were never built to solve the second.
The frame empties.
Given a steep enough deficit and no countering signal, the body spends what it can. Bone density. Lean mass. It does not casually come back.
MARROW puts it back.
Resistance training. Protein floors. Measurement you own. You arrive at your goal weight with the structure you came in with. Or better.