Adding the clinical framing, because it changes how the question reads.

DEXA scan update relevant to lean mass:

Scanned at months 0, 6, and 12. Here are the body comp numbers:

Lean mass preserved — actually GAINED 1-2 lbs thanks to progressive overload + 1.4g/kg protein. The lean mass discussion needs to include body comp data, not just scale weight.

Dr.PeteFamMed said:

Back pain as a lean mass side effect: not from the medication itself, but from rapid body composition changes.

Regarding lean mass: I accidentally injected my dose intramuscularly instead of subcutaneously last week (went in at wrong angle, too deep). Called my pharmacist — they said it's not dangerous but may absorb faster, potentially causing more GI effects.

Sure enough, had worse nausea that day. Lesson learned: pinch the skin properly and use the right needle length for your body composition.

Dr.PeteFamMed said:

Back pain as a lean mass side effect: not from the medication itself, but from rapid body composition changes.

Dr.PeteFamMed said:

...the muscle loss concern with lean mass...

This is a legitimate and well-studied concern. Let me put some numbers on it:

In STEP 1, approximately 39% of weight lost was lean mass. However, the Lundgren 2024 study showed that structured resistance training reduced this to ~25% lean mass loss.

Context matters: at BMI 35+, you're carrying excess lean mass to support the extra weight. Losing some lean mass is expected and not inherently harmful if you maintain adequate muscle function through exercise.

The solution isn't avoiding the medication — it's combining it with proper exercise and protein intake.

One thing that is still open after Dr.PeteFamMed’s answer:

Did your prescriber agree with that reading, and if not what was their objection?

Moderator note: the sourcing question belongs in the vendor section and has been split out. No action needed from anybody.