Chess is officially recognised as a sport by the International Olympic Committee

The IOC granted chess recognition as a sport in 1999, acknowledging its physical demands of concentration, psychological endurance, and competition structure. Elite chess players can burn up to 6,000 calories a day during a tournament — comparable to some physical athletes — due to the intense cognitive stress. Their heart rate, blood pressure, and respiration rates spike during critical positions.

Source: International Olympic Committee / ESPN reporting on chess physiology (2019)