Sufferers of eating disorders often hold false beliefs about their own body size. Such beliefs appear to violate norms of rationality, being neither grounded by nor responsive to appropriate forms of evidence. I defend the rationality of these beliefs. I argue that they are in fact supported by appropriate evidence, emanating from proprioceptive misperception of bodily boundaries. This argument has far‐reaching implications for the explanation and treatment of eating disorders, as well as debates over the relationship between rationality and human (...) psychology. (shrink)