Professional athletes don't get to the top by accident. It takes superhuman levels of time, dedication, and focus—and that includes paying attention to what they put in their bellies. In this series, GQ takes a look at what pro athletes in different sports eat on a daily basis to perform at their best. Here's a look at the daily diet of ultramarathon runner Dean Karnazes.

Running is the easiest sport to get into casually, because all you need are shoes and legs. As a result, there’s a lot of lore and common wisdom about the ideal runner’s diet: Everyone knows that the night before a big run—whether you’ve signed up for a 5k or a full-on marathon—you’re supposed to carbo-load on stuff like diavolo pasta, brown rice, or buckwheat pancakes.

Well... supposed to. “That’s so passé,” says Dean Karnazes.

Karnazes, 52, is an ultramarathoner who ran 350 miles—or a little less than the distance between Los Angeles and San Francisco—in 80 hours and 44 minutes; completed 50 regular, 26-mile marathons in 50 days; and wrote Ultramarathon Man: Confessions of an All-Night Runner. Come September, he’ll be hosting the third annual Navarino Challenge, a marathon in Greece meant to raise awareness of childhood obesity. And in the last 20 years of professionally being someone who runs very, very far, Karnazes has transitioned to a mostly raw diet that upends a lot of conventional wisdom about what runners need to eat to perform.

On a good day I run a marathon before breakfast.

“I used to live on junk food, thinking that since you burn 30- to 40,000 calories on some of these runs, you need to get as many calories as you can no matter how you get them in.” One time, on the solo leg of a 200-mile relay run, in the middle of the night with a cell phone and a credit card, Karnazes ordered a pizza delivered to him and kept running while he ate the whole thing in a big roll.

His running times never suffered from his diet, but his daily energy levels fluctuated wildly, so he started experimenting with different foods to see how they affected his recovery time and how they made him feel. “When you push your body that hard you get a feel for what builds you up and what slows you down.”

That intuitive elimination process led him to a diet that’s pretty close to the Paleo Diet, based on the idea that humans aren’t meant to eat anything they can’t pick from a tree, pull from the ground, or kill themselves. Karnazes’s diet isn’t as bacon-heavy as most Paleo-enthusiasts. Instead it’s heavy on fruits (VERY heavy on fruits), vegetables, cold-water fish, and yogurt. If he has any meat, it’s organic, free-range bison, usually so lightly cooked that it’s practically tartare.

The absence of oatmeal and pre-run waffles may cause skepticism, but the fact that Karnazes’s diet is enough fuel to just get him through his workouts, let alone his monster runs, is a pretty strong argument for its effectiveness. When gearing up for a big run he eats 8,000 to 10,000 calories a day. He starts with a base of 3,200 calories, and then adds 300-500 calories per hour of running.

His only real meals are yogurt at breakfast, sometimes flavored with oregano, often with fruit and nuts, and a very large dinner of salad, vegetables, and fish or bison. Most of his carbohydrates come from fruit, which Karnazes eats throughout the day whenever he’s hungry (“I think the notion of three meals a day is rubbish”). And—surprise!—he’s hungry often.

“On a good day I run a marathon before breakfast,” he says, starting off with nothing more than coffee and flax milk. After the three-and-a-half to four-hour run, he waits over half an hour to eat anything else, letting his body adjust to powering itself just on fat reserves.

One time, on the solo leg of a 200-mile relay run, Karnazes ordered a pizza delivered to him and kept running while he ate the whole thing in a big roll.

The rest of the day is constant motion. Not only are there several modified high intensity Navy SEAL workouts (push-ups, pull-ups, sit-ups, dips, and burpees) and eight to 12 miles of sprinting up hills and jogging back down, but Karnazes rarely sits. His office space is designed to work at standing-level and he’s rocking on the balls of his feet all the time, never letting his legs rest. He is almost physically incapable of staying still.

Like a hummingbird? I wonder aloud.

“Kind of like a shark,” he says.

Pre-morning runCoffee with flax milk

Post-morning runGreek-style yogurt (full fat, no sugar added) with cashews, banana and blackberries

Eaten over the course of the dayApplesPearsOranges

Food and hydration for long runsNut butterUnflavored coconut water

DinnerLarge mixed green salad with avocado, olive oil, ground ginger and turmericRaw beetsCooked sweet potato (the one vegetable eaten cooked)Wild-caught sashimi grade salmon

DessertGreek-style yogurt (full fat, no sugar added), topped with olive oil and Himalayan blue sea salt

Luke Darby is a contributor to GQ, covering news, entertainment, and the environment. A Louisiana native, he now resides in Cleveland, and his writing has also appeared in Outside, the Dallas Observer, and Marie Claire.Related Stories for GQReal Life DietHealthHealth