chris_chi24 said:

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

Physical therapist weighing in on lean mass. I work with bariatric and metabolic patients daily.

The resistance training evidence is critical here:

The Lundgren 2024 JAMA paper[1] showed that structured resistance training preserved 73% more lean mass in GLP-1 patients vs medication alone. When discussing lean mass, we MUST include the exercise component.

My minimum prescription: 3x/week compound movements (squat, deadlift, press, row), progressive overload, 7-10K steps/day, and 1.2-1.6g protein/kg/day.

AttorneyGrant said:

Agreed on the ranges, with the condition that a single DEXA is not a measurement, it is one draw from a distribution.

Genuinely useful, thank you. I had the facts and not the framework. Sending this to two other people who asked me the same thing last week.

chris_chi24 said:

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

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: -0.12 → -0.8 (stable)

No significant bone loss despite 71 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.

hans_munich said:

I lifted three times a week throughout and still lost lean mass.

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].

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