At the U.S. Sumo Open on Saturday in Long Beach, Calif., roughly 60 sumo wrestlers from around the world will face off at one of the largest sumo competitions outside Japan.

To the untrained eye, they may look like pudgy giants in underwear shoving each other around a ring. But this is a sport and there's a lot to it. Pros have to master 82 winning techniques, and follow strict training regimens that include weight lifting and flexibility exercises.

Many will be fueled by a rigid diet centered around one traditional Japanese dish called chanko-nabe. It's a stew cooked in a clay pot and is made with vegetables, chicken, pork, wild boar, beef, fish, seafood and tofu.

"Many people still think sumo wrestlers just eat fatty foods," says Yamamotoyama Ryūta, a retired 31-year-old pro who goes by Yama. "However that's not true. We eat very healthily. Rice, soup, lots of vegetables and meat. It's a good balance."

Though some sumo wrestlers are overweight or obese, many champions have a healthy ratio of muscle to fat. One champion named Byamba, for example, claims his body is just 11 percent fat.

But when it comes to these meals, we are not talking dainty portions.

At 6-foot-4 and 600 pounds, Yama is the largest Japanese wrestler the sport has ever known. To maintain a weight like that, he and other sumo athletes are eating a lot of chanko-nabe. Andrew Freund, an amateur wrestler and president of the U.S. Sumo Federation, says sumo champions and pros eat between roughly 5,000 and 8,000 calories daily. (Vice reported that one champion goes as high as 10,000 calories in a day.)

"They'll sit there and eat seven, eight or nine bowls and pack in the rice," says longtime sumo fan Ryan Goldstein. Goldstein's law firm is one of the sponsors of a Japanese stable, or group of wrestlers, called Sadogatake. "Every day they're trying to put on weight. Their goal is to bulk up so that they can't be moved or pushed around the ring."

In Japan, most wrestlers live, train and eat together in sumo stables. A typical day might start at 5 a.m. Wrestlers with less experience arise to practice before they prepare chanko-nabe for the higher ranked wrestlers. After the senior wrestlers finish training, the entire stable eats the soup together before all the wrestlers go down for a nap. Then they polish off more bowls again at dinner.

There are at least 100 different kinds of chanko-nabe and each stable has its own signature stew. Sadogatake regularly serves its hot pot with chicken and cabbage in a salt broth, especially on the first day of a tournament. Chickens stand on two feet, which is a winning position in sumo, the thinking goes.

"It's really a food that's steeped in tradition and steeped in community because we eat it together as a team even though our wrestlers will have to fight one by one during the tournament," says Machiko Kamatani. She and her husband run the Sadogatakestable outside Tokyo.

The U.S. Sumo Federation says more and more Americans are interested in sumo. But not all of its newest converts have a taste for chanko-nabe.

Natasha Ikejiri, who has won the women's middleweight U.S. Sumo Open title five times, opts for peanut butter-and-jelly sandwiches, Brazilian cuisine and sushi over the stew.

"It's really filling and it's really good but I've got to make sure that I'm not looking like a sumo wrestler," Ikejiri says.

Lightweight U.S. Sumo Open champ Jenelle Hamilton isn't a fan either: "I'm Italian. I eat pasta."

But Angel Castillo, who will compete in the US Sumo Open men's lightweight category on Saturday, treats himself to the sumo soup before big tournaments.

"Chanko-nabe can be good for any kind of competitive grappler or athlete's diet because it's just full of nutrients and protein and it's really good for post-workout recovery," Castillo says.

This story was produced in collaboration with KCRW's Good Food and the Independent Producer Project.

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