Last year, the 28-year-old San Jose, Calif., man nicknamed "Jaws" won with 62 hot dogs. He bested his main rival this year by 16 dogs, scarfing down all 68 in 10 minutes in the sweltering summer heat to take home $10,000 and the mustard yellow belt.
"I feel good, it was a great win," Chestnut said after the contest, adding he wished he could have eaten a record number of hot dogs for the audience. "I tried my best. I'm looking forward to next year already."
Second place went to Tim Janus of New York with 52 hot dogs, who received $5,000. Third place went to Patrick Bertoletti of Chicago with 51, who won $2,500.
Chestnut was neck-and-neck with competitors during the first half of the contest, but he pulled ahead in the remaining minutes, choking down dog after dog, while other competitors slowed as the clock wound down.
"I'm happy to come out with the win," he said.
Sonya Thomas, of Alexandria, Va., downed 45 hot dogs to win the women's competition. She reached her goal of eating 45 in the time limit - her age - and took home her own pink champion's belt and $10,000.
Thomas, known as the "Black Widow" of competitive eating, won last year as well, the first time a separate contest was held for women. Juliet Lee, of Germantown, Md., took second place with 33 and won $5,000. Lee also won second place last year. Third place went to Michelle Lesco, of Tuscon, Ariz., who received $2,500 for downing 25½.
Thomas said she started to feel sick while eating but kept pushing so she could win the title.
"There is a limit so I have to fight," she said.
Thomas said next year she's going to beat her record again and eat 46.
"Because I'm going to be 46 next year," she said.
The Nathan's Famous Fourth of July International Hot Dog Eating Contest has been a city tradition for 97 years. Tens of thousands of spectators gather to gawk as contestants shimmy, slither and bounce as they dip hot dogs in water and cram them down their throats.
For some, it's a painful reminder of excess - especially as the U.S. battles a growing obesity problem. The American Medical Association opposes competitive eating, saying it's harmful to the human body. But the competitive eaters are quite trim. Chestnut is more than 6 feet tall and a muscly 210 pounds, and Thomas, who is 5-foot-5, weighed in at barely 100 pounds.
Hot dogs, though, aren't the healthiest of choices. In addition to beef, they include salt and various food additives. Chestnut's total dog count was equal to more than 20,000 calories. This year, the animal rights group Mercy For Animals staged a protest against eating meat, with signs that read "Choose Vegetarian."
Chestnut is now tied with his former rival, Takeru Kobayashi, for consecutive wins. The slim Japanese champ held the record for hot dog eating from 2001 to 2007, when he was unseated by Chestnut.
But two years ago, after refusing to sign an exclusive contract with Major League Eating, the food equivalent of the NFL, he was banned from competition. He showed up anyway, wearing a T-shirt that said "Free Kobi," rushed the stage and was arrested, but charges were later dropped.
Last year, the Japanese native nicknamed the "Tsunami" held an unofficial contest from a rooftop on ritzy Fifth Avenue, eating near a giant plasma TV airing the official competition live.
Kobayashi competed in a different eating contest on Wednesday.
Associated Press videographer Bonny Ghosh contributed to this report.
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