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The competitive-eating elite will descend on New York City’s Coney Island this Fourth of July to flex their hot dog eating skills at the annual Nathan’s Famous Hot Dog Eating Contest. Last year, the male winner ate 62 hot dogs and the female winner ate 38 hot dogs in 10 minutes. Competitive eaters are surprisingly slight for the enormous amount of food they are able to consume. Where do all those hot dogs go?

The stomach is not a passive sack but an active organ that expands and contracts. An empty stomach holds about 1/4 cup, but when a meal is swallowed, the stomach expands to hold as much as 6 cups without stretching its walls. Besides relaxing to hold the meal, the stomach’s walls squeeze in and out and back and forth to move the food into the intestines, a process called gastric emptying. Researchers at the University of Pennsylvania wondered if speed eaters’ ability to keep down so many hot dogs was because their stomachs emptied faster or if their stomachs were trained to hold much more food than the average person.

The researchers recruited a professional speed eater and compared his gastric physiology to an individual with a big appetite. A gastric emptying test revealed that the professional speed eater’s stomach emptied slower than the regular eater. After 10 minutes, the regular eater consumed seven hot dogs, and his stomach was not stretched out. In contrast, the speed eater ate 36 hot dogs, and his stomach became a “massively distended, food-filled sac occupying most of the upper abdomen,” the researchers wrote. While the regular eater felt sick, the speed eater said he didn’t feel full, leading the researchers to wonder if the competitive-eating training made the stomach so stretchy and limp that the competitors never get the “full” physiological signal.

Although the study examined only one professional speed eater, the results support the idea that competitive speed eaters could eat large amounts of food in short periods of time not because their stomachs emptied faster but because their stomachs were able to enlarge dramatically.

The record for most hot dogs eaten is 69. How does the stomach look after that many? Not great, this video from ESPN shows.

Maggie Kuo, PhD, is the former Communications and Social Media Coordinator for APS. Catch more of her writing in the Careers Section of Science Magazine.