No one who understands how much 6,000 calories is could make this claim.

That would mean they need to eat 8,000 calories a day for a normal 2000 calorie diet. That's like Michael Phelps level. That's like: leave the tournament, go back to your hotel and eat 7-8 medium dominos entire pizzas in a sitting. I hope I don't need to explain that this is not what chess masters are doing.