Adam Strandberg works on metabolism and has run into the claim that chess grandmasters burn 6000 calories per day during tournaments:
I assumed when I dug into it that I would find a specific methodological error. But while methods enter the story, the real problem is that the number was completely made up.
As far as I can tell, the “patient zero” that caused this claim to become so widespread is this 2019 ESPN article:
Robert Sapolsky, who studies stress in primates at Stanford University, says a chess player can burn up to 6,000 calories a day while playing in a tournament, three times what an average person consumes in a day. Based on breathing rates (which triple during competition), blood pressure (which elevates) and muscle contractions before, during and after major tournaments, Sapolsky suggests that grandmasters’ stress responses to chess are on par with what elite athletes experience.
This story was then picked up by many outlets, such as CNBC, Men’s Health, Inc, GQ, Marginal Revolution, and Joe Rogan.
So the claim came from Robert Sapolsky. However, a Google Scholar search turned up no primary literature from him on the topic. Fortunately, someone on Reddit was also curious and shared an email from Professor Sapolsky explaining the number. He first references a footnote from his 1994 book Why Zebras Don’t Get Ulcers:
The definitive study on chess players was carried out by the physiologist Leroy DuBeck and his graduate student Charlotte Leedy. They wired up chess players in order to measure their breathing rates, blood pressure, muscle contractions, and so on, and monitored the players before, during, and after major tournaments. They found tripling of breathing rates, muscle contractions, systolic blood pressures that soared to over 200—exactly the sort of thing seen in athletes during physical competition. See the original report, Leedy’s thesis, “The effects of tournament chess playing on selected physiological responses in players of varying aspirations and abilities” (Temple University, 1975) or their brief report (Leedy, C., and DuBeck, L. 1971. Physiological changes during tournament chess. Chess Life and Review, 708). In a telephone conversation, DuBeck also tells the story of the international match in the early 1970s between grand masters Bent Larson and Bobby Fischer, in which the former had to be given antihypertensive medication in the middle of his losing match; his blood pressure remained elevated for days afterward. And for that special chess fan out there who just can’t get enough of this subject, may I suggest as the perfect gift a copy of Glezerov, V., and Sobol, E. 1987. Hygienic evaluation of the changes in work capacity of young chess players during training. Gigiena i Sanitariia 24, in the original Russian.
This doesn’t say anything about calories, though the “tripling of breathing rates” matches part of the ESPN quote. He goes on:
The figure of 6K calories/day is an extrapolation that DuBeck generated, based on those measures and the typical duration of tournaments. Obviously, it’s a pretty soft, squishy number. I’d asked the ESPN people to mention that the 6K was an indirectly derived measure, the number of calories shouldn’t be presented as gospel, so if they were going to cite the 6K, they should cite these caveats as well. But I guess the caveats didn’t make the editing process…
Hope that helps.
Robert Sapolsky
[…]
To summarize: a grad student took physiological measurements of 11 ordinary chess players (not grandmasters). They reported in a summary in a chess magazine that the maximum chest movement rate they measured in a 10 second period was almost three times that of an average measurement from a different study. Robert Sapolsky then cited this thesis in his popular book, dropping the distinction between maximum and average to give a 3X breathing rate. He later took the 3X number and multiplied that by 2000 calories per day to get the number 6000, adding the “grandmaster” rhetorical fluorish along the way. He spread this fact through his own talks at Stanford and through interviews with journalists, who accurately repeated him. When questioned about the source of the number, he then claimed on multiple occasions that the number actually came from someone else, and that journalists had distorted his argument.
One remembers Harvard professor Wilson’s claim, made up for rhetorical emphasis, that something like 40,000 special go extinct each year due to human activities, especially habitat destruction.