Nitrogen Sparing Thermogenics

Does anyone know the mechanism by which ephedrine and HOT-ROX are “nitrogen sparing”?

i think i have read that both make fat stores more readily available for energy, it it just a side effect of having more non - protein energy sources in the blood?

Yes, although HOT-ROX also works by a similar mechansim to Carbolin 19, which adds another potential muscle-sparing benefit.