The ECA stack is a thermogenic sports supplement containing ephedrine, caffeine, and aspirin — a combination once popular with bodybuilders and dieters for fat loss. The logic was pharmacological synergy: ephedrine stimulates the sympathetic nervous system, raising metabolic rate and suppressing appetite; caffeine amplifies the stimulation and prolongs ephedrine’s action; aspirin was added to further extend the thermogenic effect. Users reported real short-term weight loss, but the cardiovascular cost was serious — raised blood pressure and heart rate, arrhythmias, strokes, and deaths led regulators to restrict or ban ephedrine in supplements across many countries. The ECA stack’s history is a cautionary tale of sports nutrition: a combination with genuine pharmacology, genuine risks, and a risk-benefit balance that regulators ultimately judged unacceptable.