Chess grandmasters spend hours sitting over game boards. And yet, high-level players lose 10 to 12 pounds on average over a 10-day tournament. ESPN’s Aishwarya Kumar dug into that statistic.

AUDIE CORNISH, HOST:

Chess grandmasters spend hours facing off over game boards. Beyond extending their hands to move pieces or maybe tipping their heads to the side in thought, it really just involves a lot of sitting. And yet, those playing at the highest level lose 10 to 12 pounds, on average, over the course of a 10-day tournament. Now, that improbable statistic was enough to send ESPN’s Aishwarya Kumar down a rabbit hole. She had to know why a mental game takes such a physical toll.

Aishwarya Kumar, welcome to the program.

AISHWARYA KUMAR: Thank you for having me.

CORNISH: Let’s start with the idea of this weight loss or calories burned. How does this compare to other athletes in other sports?

KUMAR: One of the basic facts was the 1984 World Chess Championship, right? So after five months and 48 games, defending champion Anatoly Karpov had lost 22 pounds. And some people said he looked, like, dead. Chess players were burning calories around the same rate as tennis players and competitive marathon runners. Like, in October 2018, Polard, this company that tracks heart rates, monitored chess players during a tournament and found out that this 21-year-old Russian grandmaster, Mikhail Antipov, had burned 560 calories in two hours, which we found out was roughly what Roger Federer would burn in one hour of singles tennis.

And I talked to Robert Sapolsky. He’s been studying primates for a long time now, and he corroborated that fact and said that, you know, chess players can burn up to 6,000 calories in a day by playing a tournament, which is three times that of any human on a regular day.

CORNISH: Now, what did you learn about why? Is it that their brains are just using that much energy, or is there something physiological going on?

KUMAR: Yeah. So the brain obviously is functioning at a much higher level, but we should understand that the brain alone is not causing the weight loss. The brain’s metabolism is causing for different reaction to occur in your body, like increased stress, like loss of appetite, like disturbed sleep patterns. And because of all of these different factors that the brain is setting off – that is the reason they’re losing weight.

CORNISH: I want to talk about world champion Magnus Carlsen from Norway. You learned about his training regimen. Tell me about the moment he realized that he needed a competitive edge and what he did to get it.

KUMAR: Yeah. So it’s interesting with Magnus Carlsen – he realized early on that fixing small things, like what he drinks during the course of a game, will alter the way he functions, especially in the last hour or so of the game. And so one of the things that was really fascinating about this was when I was talking to his dad. His dad was like, oh, we went to the Olympic Training Center. And they were told immediately that the orange juice that he was drinking was causing for the sugar levels to take a huge dip in the fifth and sixth hours of game. And so they were asked to replace that with milk.

CORNISH: Meaning he’d have a little energy crash. So the idea is you need to keep yourself sustained with something that gives you energy but won’t have the crash and that you need to do that even if you’re not skiing, right…

KUMAR: Exactly. Exactly.

CORNISH: …Even if you’re playing chess. So as we look at the world cup of chess, which is happening right now, what are you going to be watching for? What are the things you’ll see and you’ll think, that’s somebody who’s using some training?

KUMAR: I am actually very interested to see how they are sitting because another interesting thing that I found out during the course of the reporting was just how important the posture was. And Magnus Carlsen has perfected the sitting posture that has helped him. He taps his foot gently to keep his alertness on the highest level while still not losing too much energy. He chews gum. So I want to, you know, pay attention to all of those small details during the world cup to be like, OK, you’re – you know, you’re paying attention to all of these smaller elements that’ll set you apart from the rest of the crew.

CORNISH: That’s Aishwarya Kumar, international writer for ESPN. Thanks for explaining it to us.

KUMAR: Thank you so much for having me.

Copyright © 2019 NPR. All rights reserved. Visit our website terms of use and permissions pages at www.npr.org for further information.

NPR transcripts are created on a rush deadline by Verb8tm, Inc., an NPR contractor, and produced using a proprietary transcription process developed with NPR. This text may not be in its final form and may be updated or revised in the future. Accuracy and availability may vary. The authoritative record of NPR’s programming is the audio record.