The chess thing was based on a misconception. Someone measured chess players heart rate and saw that it was increased, then compared that pulse rate to athletes

The chess thing was based on a misconception. Someone measured chess players heart rate and saw that it was increased, then compared that pulse rate to athletes training and basically said they must be burning as many calories since they had the same heart rate. This study gives a much more reasonable estimate of calorie expenditure: https://www.researchgate.net/publication/23455094_The_stress_of_chess_players_as_a_model_to_study_the_effects_of_psychological_stimuli_on_physiological_responses_An_example_of_substrate_oxidation_and_heart_rate_variability_in_man https://www.researchgate.net/publication/23455094_The_stress...