Why three receptors matters — GCG arm for lipolysis, not just weight
212 posts
People talk about reta as 'tirze plus.' It's not. The glucagon receptor agonism does something tirze literally cannot do — direct lipolysis and increased resting energy expenditure.
Mechanism in brief: GCG receptor activation on adipocytes upregulates HSL and ATGL → releases FFAs → hepatic oxidation. Plus increased thyroid conversion (T4→T3) peripherally. That's why reta runs you warmer and why fat loss composition may differ from pure GLP-1 class.
Practical implications:
- Muscle sparing may be better than tirze on high-protein intake because the energy deficit is partially pulled from fat oxidation rather than purely from appetite suppression.
- Thermogenic response means expect slightly higher kcal baseline — you can eat more and still lose.
- HR/BP bump isn't a bug, it's sympathetic activation from GCG. Watch it.
Curious what others' DEXA data says on LBM retention. This is the claim that needs testing.
- CJC-1295 no DAC · 100 mcg · pre-bed · sub-Q
- Ipamorelin · 200 mcg · pre-bed · sub-Q
- BPC-157 · 500 mcg · 2x/day · sub-Q
11 Replies
38 posts
Protein intake across both cycles? LBM retention is downstream of protein + training volume more than compound choice. If your protein was lower on tirze it skews the comparison.
47 posts
I have DEXA at 0/8/16 on both tirze (last year) and reta (ongoing, through week 12 so far). Tirze: lost 22lb, ~3.5lb LBM. Reta: lost 18lb through week 12, 1.8lb LBM. Too early to call but the trend matches what you'd predict from GCG-driven fat oxidation.
117 posts
The GCG → lipolysis mechanism is solid in rodent and ex vivo data. Human in vivo contribution at therapeutic reta doses is less characterized — some of the thermogenic effect people feel may be central (hypothalamic) rather than peripheral lipolysis. Mechanism is plausible but 'how much' is the open question.
47 posts
@macrosguru same macros (2g/kg protein), same training (4x/week upper/lower), same sleep tracking. Not RCT-clean but as controlled as a self-experiment gets.
30 posts
The thermogenic subjective thing is real — I said it in another thread, I literally sweat more on reta. Sympathetic activation is the most parsimonious explanation.
45 posts
The 'muscle sparing may be better' claim needs a lot more n. @dexa_devotee's data is encouraging but one subject. Anyone else with paired DEXA across classes?
43 posts
I'll have paired data in ~8 weeks. Finishing tirze DEXA now, starting reta February. Same training, same macros. Will post.
212 posts
@citation_required fair, I softened it too little. The thyroid angle is hypothesis not established. Peripheral oxidation bump is the durable claim.
- CJC-1295 no DAC · 100 mcg · pre-bed · sub-Q
- Ipamorelin · 200 mcg · pre-bed · sub-Q
- BPC-157 · 500 mcg · 2x/day · sub-Q
71 posts
The T4→T3 conversion bump claim is softer than the lipolysis one. Some signals but human data is thin. Don't want readers walking away thinking reta is a thyroid modulator — that's overreach.
40 posts
Real talk, the muscle sparing angle is worth testing but the way it's framed here is backwards. You don't spare muscle because fat oxidation goes up, you spare muscle because you're not starving yourself into a deficit. Reta just lets you eat more without hunger signaling your brain it's dying. Same protein intake, same training, same LBM retention as tirze probably. The thermogenic stuff is legit but that's not why your arms don't shrink.