Distinct molecular routes to raised energy expenditure
Thermogenic compounds increase energy expenditure through separate pathways rather than a single shared mechanism. Caffeine blocks adenosine receptors and inhibits phosphodiesterase, prolonging catecholamine signaling. EGCG from green tea slows the breakdown of norepinephrine by inhibiting COMT. Capsaicin activates TRPV1 channels and can recruit thermogenic activity. Forskolin raises cyclic AMP by acting on adenylate cyclase. Synephrine is a mild beta-adrenergic agonist. Cold exposure works through sympathetic activation of brown fat.
Because the routes differ, the diagram contrasts where each agent enters the chain rather than implying they are interchangeable.
Why measured effects stay modest
In human studies the increase in daily energy expenditure from these compounds is typically small, often a few percent, and tolerance to caffeine and synephrine develops with regular use. Several carry cardiovascular considerations: synephrine and high-dose caffeine can raise heart rate and blood pressure.
This is general educational information, not medical advice. Stimulant thermogenics are not appropriate for everyone, and anyone with heart conditions, hypertension, or who takes interacting medication should consult a clinician before use.