Kobayashi set his first record at his rookie appearance on July 4, 2001, when he ate 50 hot dogs in 12 minutes at the Nathan's Coney Island hot dog-eating contest, doubling the previous record of 25. The record was so unexpected that when Kobayashi got to the later numbers, the organizers ran out of signs indicating how many dogs Kobayashi had eaten and had to resort to handwritten signs. In 2002, he broke his own record by eating 50.5. In 2003, he won again by eating 44.5. In 2004, he triumphed again by eating 53.5 hot dogs in 12 minutes, beating his old record. There was a small controversy over this result, as some fellow competitors accused him of regurgitating during the 12-minute competition. Though regurgitation is not explicitly prohibited, once food enters the mouth of the contestant, it is not permitted to exit. In 2005, he managed to eat 49 hot dogs and win his fifth straight contest. In 2006, he ate 53.75 hot dogs for his sixth consecutive win and a new world record.
On June 2, 2007, Joey "Jaws" Chestnut broke Kobayashi's record with 59.5 hot dogs and buns in a qualifying round for the annual Nathan's contest
In the 2006 Krystal Square Off, Kobayashi's mark of 97 hamburgers was 30 better than his winning total in 2005 and 28 better than the World Record he set in 2004.
At a speed-eating contest in Hong Kong on August 13, 2005, Kobayashi consumed 83 vegetarian jiaozi dumplings in 8 minutes. The next day, he ate 100 roasted pork buns in 12 minutes.Kobayashi also won the 2005 Alka-Seltzer US Open of Competitive Eating, a three-hour IFOCE elimination tournament on ESPN, as well as the Glutton Bowl, a two-hour IFOCE eating special that aired on the Fox Network in 2002. However, on Fox's 2003 show Man vs. Beast, Kobayashi lost in an eating competition against a 1089-pound Kodiak bear, when he ate 31 bunless hot dogs in 2 minutes and 36 seconds to the bear's 50.
On August 5, 2006, Kobayashi set yet another world record at the Johnsonville World Bratwurst Eating Championship in Sheboygan, Wisconsin, by downing 58 bratwurst sausages in 10 minutes, shattering the previous record of 35 set the previous year by Sonya Thomas.
On September 23, 2006, Takeru Kobayashi set the world record at the Phantom Food Festival in Boston, Massachusetts, for eating 41 Summer Shack lobster rolls in 10 minutes, replacing the previous record of 22 rolls.
Other world-eating records held by Kobayashi include 17.7 pounds of cow brains in 15 minutes and 20 pounds (9 kg) of rice balls in 30 minutes.
On June 25, 2007 Kobayashi announced on his blog that he seriously injured his jaw during training. He stated that he can only open his jaw about the width of a fingertip. Kobayashi's participation in the July 4, 2007 Nathan's contest continued as scheduled. He was able to eat a personal record 63 hot dogs, though his mark was bettered by Joey Chestnut who ate 66.
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