No Calorie Receptors: Why the Behavioral Control of Food Intake Tracks Mass, Not Energy

Behavioral and sensory research on food intake has long treated energy content as if it were a directly perceptible property of food. Organisms are said to “detect,” “evaluate,” or “compensate for” calories. This language imports an energy-centric ontology into a sensory system that has no access to energy as such. There are no receptors for the joule or the kilocalorie. Taste, smell, texture, oral processing, and gastric distension respond to molecular identity, physical mass, volume, and structure. Post-ingestive signals report molecular identity and concentration, not energy content. Energy is a derived quantity that can be associated with sensory patterns through learning, but it is not sensed directly. The present commentary argues that this category error – a derived property treated as a perceptible one – has shaped experimental design, interpretation, and vocabulary in the behavioral literature, and that restoring mass to primacy brings the psychology of appetite into register with the physics and physiology of mass balance.