paige_pharma said:

Physical therapist weighing in on lean mass.

Body composition tracking via bioimpedance on lean mass (InBody scan every 3 months):

Note: skeletal muscle mass dipped initially then recovered with consistent resistance training + high protein. The visceral fat reduction is where the metabolic magic happens.

maria_elpaso said:

Right, and protein targets should be set on a reference weight rather than current weight.

Thank you — that is the clearest version of this I have read, and I have read a lot of them. I will report back once I have actually tried it.

paige_pharma said:

Physical therapist weighing in on lean mass.

Bone density monitoring on lean mass: DEXA bone density at baseline and month 12.

Lumbar spine T-score: -0.9 → -0.7 (stable to slightly improved)
Femoral neck T-score: -0.10 → -0.8 (stable)

No significant bone loss despite 51 lbs of weight loss. Key factors: adequate calcium (1200mg/day), vitamin D (5000 IU/day), resistance training 3x/week, and adequate protein. Weight-bearing exercise is critical for maintaining bone density during rapid weight loss.

sarah_TO said:

Two DEXA scans eleven months apart: down 24kg total, of which the scan says 6kg was lean.

Muscle fiber type changes during GLP-1-mediated weight loss, relevant to lean mass: preliminary biopsy data suggests that weight loss shifts the skeletal muscle fiber type distribution:

• Decreased Type IIx (glycolytic, fast-twitch) fibers
• Increased Type I (oxidative, slow-twitch) fibers
• Improved mitochondrial density and function
• Enhanced insulin-stimulated glucose uptake per fiber

This "metabolic remodeling" of muscle may contribute to improved insulin sensitivity independent of total lean mass changes. The muscle you keep becomes metabolically better, even if there's less of it[1].

Moderator note: two posts asking for a source have been merged into one. Please search the thread before asking again.