JenPlateau said:Body composition tracking via bioimpedance on lean mass (InBody scan every 3 months): Metric Baseline Month 3 Month 6 Month 9 Skeletal Muscle (lbs) 70…
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].
[1] Pirkmajer S, et al. Front Physiol. 2023;14:1123456.
DeniseRN_TPA said:Agreed on the ranges, with the condition that a single DEXA is not a measurement, it is one draw from a distribution.
Thank you for spelling out the reasoning rather than just the conclusion. Printing the relevant bit and taking it with me.
JenPlateau said:Body composition tracking via bioimpedance on lean mass (InBody scan every 3 months): Metric Baseline Month 3 Month 6 Month 9 Skeletal Muscle (lbs) 70…
JenPlateau 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.
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Shop Reference Standardsemily_PDX said:Two DEXA scans eleven months apart: down 24kg total, of which the scan says 6kg was lean.
Sharing my comprehensive lab data relevant to lean mass:
| Biomarker | Baseline | Month 3 | Month 6 | Month 9 |
|---|---|---|---|---|
| Weight (lbs) | 255 | 250 | 225 | 215 |
| A1C (%) | 6.5 | 6.5 | 6.0 | 5.2 |
| hsCRP (mg/L) | 5.0 | 3.0 | 2.5 | 1.1 |
| Triglycerides | 235 | 185 | 115 | 105 |
Protocol: Tirzepatide 15mg/wk, resistance training 4x/week, protein 1.6g/kg/day.
The improvements in lean mass are clearly reflected in these numbers. The inflammatory marker reduction (hsCRP) is particularly striking.