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Joey Chestnut. Photo: AP

The world’s greatest eaters are about to converge on Brooklyn for the annual Fourth of July hot-dog eating contest. As you’ll no doubt recall, Joey Chestnut snatched the title last year from the great Takeru Kobayashi by eating 66 hot dogs and buns in 12 minutes.

For the Health Blog, this raises a fundamental question: How can anyone (much less these guys, who aren’t particularly large of belly) choke down that many hot dogs that fast?

Fortunately, we aren’t the only ones who wanted to know.

“The question was, do they empty their stomach really rapidly or does their stomach blow up like a balloon?” Marc Levine, a radiologist at the University of Pennsylvania, told us in a recent phone conversation.

Levine was an author of a study published last year in the Journal of Roentgenology — “Competitive Speed Eating: Truth and Consequences” — that provides something of an answer.

Levine and his colleagues took two guys. One of them was a champion eater, ranked in the top 10 in the world, who was 29 years old, 5′10″ tall and weighed 165 pounds. The other was just some guy who “had a hearty appetite.” He was 35 years old, 6′2″, 201 pounds. (The doctors wound up doing this because the National Geographic channel was shooting a special on the science of speed eating; the University cleared the whole thing, and the eaters went through the standard consent process for human-subject research.)

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Stomach of a normal eater who felt full after eating seven hot dogs. Arrows indicate hot dog bits. (Image courtesy Marc Levine.)

The regular guy went first, and stopped after seven dogs (no buns, for purposes of the study) because he thought he’d be sick if he ate another. Using fluoroscopy, an x-ray that gives a real-time view of what’s going on inside the body, the doctors saw what you’d expect: His stomach was indeed full of hot dogs and hadn’t stretched much from its original size (see picture at left).

Then they looked at the competitive eater. First, they noticed that his empty stomach showed virtually no peristalsis, the normal squeezing motion that helps the stomach break down food. He started eating hot dogs and his stomach got bigger and bigger. Ten minutes in, he’d eaten 36 dogs. He said he didn’t feel full, but the researchers told him they’d seen enough.

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Stomach of a champion eater, after eating 36 hot dogs in 10 minutes. (Image courtesy Marc Levine)

“His stomach now appeared as a massively distended, foodfilled sac occupying most of the upper abdomen, with little or no gastric peristalsis,” they wrote in their paper. Levine said the stomach was like no healthy stomach he’d seen in his 30-year career. He compared it to a “giant balloon that looks like it has no limit.” The eater’s previously flat belly swelled out as if he were pregnant.

The champion told the doctors he had “spent several years training for the sport, forcing himself to consume larger and larger amounts of food despite the sensation of fullness.” He said he never felt full anymore. They figured the training had somehow given the guy’s stomach this ability to expand indefinitely.

They also suggested that, if the eater in their study were representative of others in the sport, there was a long-term risk that the stomach could lose its ability to return to normal size, which could cause serious problems, such as persistent nausea and vomiting that could ultimately require surgery. In our conversation, Levine emphasized that those risks were largely speculative — but he said they couldn’t be ruled out.

Major League Eating, which sponsors the hot-dog contest along with the hot-dog seller Nathan’s Famous, explicitly prohibits home training. And the group’s chairman, George Shea, told us he isn’t aware of any problems that the study says are theoretically possible ever actually occurring.

“There’s a small risk in competitive eating, but I think it is much smaller than in other sports,” he told us. “If you compare that to motocross, NASCAR or football, our risk would be marginal in comparison. Are we a greater risk than ping pong? I would say yes.”