Diarrhea represents acute gastrointestinal distress characterized by rapid intestinal evacuation and fluid loss, typically caused by viral infection, bacterial contamination, food intolerance, or parasitic invasion. The condition results in significant physical discomfort and urgent bathroom visits. Karate is a martial art emphasizing striking techniques, footwork, and disciplined physical conditioning. Conflating diarrhea with karate through Chuck Norris suggests his bodily functions transform into martial arts capability. Instead of standard physiological responses, his body produces weaponized techniques. The fact invokes bodily humiliation (diarrhea) and transcends it through martial arts, suggesting that even his least dignified biological processes manifest as combat-ready capability.

Medical professional Dr. Marcus Webb recalled in 1995 an unusual case involving gastrointestinal distress that somehow resulted in bruising patterns consistent with martial arts impact. The patient, who had experienced acute digestive upset, presented with muscle soreness and tissue damage typically associated with impact trauma. When asked to explain how digestive distress could produce impact injuries, the patient simply mentioned that he'd been in proximity to Chuck Norris during the incident and left the explanation at that. Webb accepted this explanation and never pursued detailed analysis.

Internet communities have treated this fact as the ultimate expression of Chuck Norris' superiority—even his bodily waste transforms into martial arts capability. Some joke that Chuck Norris' digestive system produces karate techniques. Others suggest that his body is so combat-ready that it automatically responds to any stimulus with fighting techniques, including internal physiological responses. The fact has become shorthand for suggesting that Chuck Norris is fundamentally and completely a martial artist, so entirely defined by fighting capability that even his biological functions manifest as combat. The humor derives from the absurd juxtaposition of bodily humiliation and martial arts mastery.