Jack Osbourne (search), the chubby, bespectacled son for former shock-rocker Ozzy Osbourne (search), underwent almost four weeks of training and colonic irrigations before entering the ring against a veteran Thai kickboxer.

The result: a second round knockout win to the teenage television personality.

Ozzy and Sharon Osbourne, respectively the muddled patriarch and prickly matriarch of the family whose life was documented in the hit reality show "The Osbournes," flew in to see Wednesday night's big bout, which was over in less than four minutes, a family associate said.

Jack, 19, who underwent drug rehabilitation in 2003, came to Thailand to learn the traditional sport — called muaythai — to help him get in shape for an upcoming rock climbing expedition in the U.S. said Ed Stobart, a Briton traveling with the young Osbourne.

"He has been training very hard for three and-a-half weeks," Stobart told The Associated Press in a telephone interview on Thursday. "His mum and dad flew in on what is essentially a private visit to see him and they're having a family day today."

Jack spent four days at the elite Fairtex Muaythai Fitness Camp near Bangkok, the Thai capital, before traveling to the popular tourist island of Pha-Ngan for "a complete physical detox, which was basically twice-daily massive colonic irrigations to kind of flush himself out of toxins," Stobart said.

Jack returned to the boxing camp for 10 more days of training before facing off against an experienced Thai boxer known only as "The Man."

With Ozzy and Sharon cheering him on, Jack knocked his opponent out eight seconds into the second round, said Philip Wong, Jack's trainer. Muaythai fights usually have five three-minute rounds.

"I was very impressed with his training," said Wong. "He behaved and he trained so hard for it ... he lost 20 pounds when he was with me."

But Jack, quoted by The Nation newspaper, said he needed to lose another 10 pounds to achieve his best fighting weight.

Jack took up muaythai after deciding to clean up his alcohol and drug habits and get healthy, an endeavor supported by his father, who also gave up drinking last year, the Nation reported.

"At first mum and dad were a little concerned," Jack was quoted as saying. "But once they came here and saw the training programs — and saw for themselves that I was mentally and physically well prepared — they were very cool about it all."

Jack said he enjoys sports that test his mind, body and spirit.

"I'd have to say that muaythai is something special. It's really demanding and it's becoming popular all around the world," he said.

Jack owes his fame to the MTV show "The Osbournes," which follows the lives of Ozzy, the former lead singer of legendary British heavy metal band Black Sabbath (search), and his wife, son and daughter. The show is in its final season.