LOS ANGELES — Matt Haag, a professional video game player, makes close to a million dollars a year sitting in a soft chair smashing buttons. It is a fantastically sweet gig, and he will do about anything to keep it.

That is why, on a recent morning, he was in a bungalow in Venice Beach, Calif., making pancakes. Not just regular pancakes, but high-protein pancakes with ingredients like flax oil and chia seeds, whose balance of carbohydrates, fat and protein was created by a dietitian hired to teach him how to eat more healthily.

The pancakes were just the beginning of a monthlong training session that Red Bull, one of Mr. Haag’s sponsors, organized for him and his team, OpTic Gaming. Over the next several days, he and his fellow players gave blood while riding stationary bicycles, had their brains mapped by a computer and attended an hourlong yoga class where they learned, among other things, how to stretch their throbbing wrists. The purpose of all this: to help them get better at blowing their opponents away in video games.

Three years ago, he was flipping burgers at McDonald’s. Today Mr. Haag, 22, skinny and blindingly pale, makes his living playing Call of Duty, a popular series of war games where players run around trying to shoot one another.