Producing loss of appetite, a synonym for anorectic used in pharmacology and physiology to describe substances that reduce the drive to eat. The body’s own anorexigenic signals include the gut hormones peptide YY and GLP-1 released after meals, and the adipose hormone leptin, which together tell the brain that enough food has been consumed. Pharmaceutical research has focused intensely on mimicking or amplifying these signals, yielding the GLP-1-based drugs that have transformed obesity treatment. The term also describes the appetite-killing effects of illness, stress hormones, and certain medications, effects that clinicians must manage in patients who need to maintain nutrition during treatment. Understanding anorexigenic pathways has moved appetite from a matter of willpower to a matter of measurable, manipulable biology.