A 57-year-old man developed severe heart failure with 15% ejection fraction after losing 26 kg in just two months using 0.25 mg semaglutide, combined with decades of nicotine replacement therapy at 30-40 mg daily. His heart showed global dysfunction, marked dilation, and fibrosis despite normal coronary arteries and negative cardiomyopathy workup. This case illuminates a critical blind spot in the weight-loss revolution. While semaglutide and similar GLP-1 agonists have transformed obesity treatment with remarkable efficacy, the cardiac safety profile during extreme weight loss remains poorly understood. The heart muscle appears vulnerable to severe energy deficit, particularly when pharmacologically driven appetite suppression enables sustained caloric restriction beyond physiological tolerance. This represents more than typical cardiac risk from obesity drugs—it suggests the myocardium itself may fail under metabolic stress from overly rapid weight reduction. Given millions now using GLP-1 therapies, understanding the threshold between beneficial weight loss and dangerous energy depletion becomes paramount. The case demands urgent research into optimal weight-loss velocity and cardiac monitoring protocols for patients achieving dramatic results on these powerful medications.