On his way to becoming one of the top chess players in the world, Danny Rensch learned a tough lesson in just how physically demanding the game can be. “Seven hours into a game, I made a blunder that made me realize I had basically not eaten anything for the past seven hours and was only drinking water,” he recalls. “All my blood sugar dropped, and I was shaking; I had to go to the hotel gift shop and buy whatever I could get to restabilize my levels.”
According to Rensch, who is now the Chief Chess Officer of chess.com, this experience is fairly common among chess players. “That’s our genetic evolution. You don’t think about eating or calming down when you’re running from the tiger,” he says. “A lot of chess players have that moment, where they realize they hadn’t appreciated the need to physically prepare before a game.”
Per neurologist Robert Sapolsky, chess grandmasters can burn 6,000 to 7,000 calories a day during a high-level tournament — or roughly the equivalent of a marathon runner — because even though they’re sitting still, they’re “turning on a massive physiological stress response simply with thought.” Sapolsky told ESPN in 2019 that chess grandmasters’ breathing rates, elevated blood pressure and muscle contractions are “on par with what elite athletes experience.”
Rensch can attest to that. “Chess has a level of intimate stress that’s arguably unmatched by any other sport on the planet,” he says. “I’ve both lost and won games simply because one of us got exhausted. Exhaustion leads to blunders, so outlasting your opponent is a big part of the strategy.”
In the weeks leading up to a tournament, many chess players will focus on training their physical endurance and improving their overall health. “A lot of times the focus is on practical things that make you a great athlete — energy levels, exercise, eating right, getting on a good sleep schedule,” Rensch says. “Today’s players are aware of the stamina and physical upkeep needed in order to maintain the level of effort and focus they need to in a long, grueling game.”
So grueling, in fact, that the second best player in the world, Fabiano Caruana, said in an interview with ESPN that he often expects to lose 10 to 15 pounds over the course of a tournament.
When the end goal is to “maintain a physical condition that allows for high amounts of mental exertion,” Rensch says most training days begin with a morning “stamina-building exercise, such as running a 5K, rowing or swimming. Before or after your run, row or swim, should be a balanced breakfast that will “fuel the body with lasting energy,” Rensch explains. For example, a dedicated chess player’s breakfast could include two eggs, three ounces of salmon or smoked fish, one cup of oatmeal or grains and one cup of whole fruit.
After breakfast, players turn their exercise routine to the mind, spending two to three hours “solving complex chess puzzles and working on the practical skills of chess.” Next up comes a lunch that’s packed with protein and enough carbs to provide stable energy throughout the rest of the day — a la “a small serving of chicken or beef, topped with avocado, walnuts or pumpkin seeds.” Small, however, is the operative word here. “Players are at peak focus, releasing and using the right amount of adrenaline when their body isn’t focused on digesting during the game,” Rensch tells me.
Then it’s back to some “extended cardio” — e.g., the two top chess players in the world are known to spend an hour every day playing tennis, basketball or soccer. From the tennis or basketball court (or soccer pitch), they immediately return to intensive chess training for another two to three hours.
Only once all of this is done — and the day is drawing to a close — do they allow their appetites to finally checkmate them. “During an event, a player will often not eat their biggest meal of the day until after the games have been played,” Rensch explains. “That’s when they should feel free to engage with all foods of their liking!”