I was hanging out with no one under 21. I thought that if I really wanted to fit in I had to... show them that I was in a way just as adult as they were, 'cause I could hold my own just as well as they could, if not better.

Osbourne lost 23 kg in Thailand at a Muay Thai martial arts camp in Pattaya in order to be fit enough to climb El Capitan (which he achieved) whilst filming the first series of Jack Osbourne: Adrenaline Junkie. Osbourne has since pursued a career as a fitness and travel reporter presenting shows such as Jack Osbourne: Adrenaline Junkie (2005-09) and BBC's Saving Planet Earth (2007). Adrenaline Junkie focuses on Osbourne's training for sports like rock climbing mountaineering and a jungle trek in Belize from the Chiquibul Chamber through dense jungle ending at Caracol ruins (Guided by the UK extreme conservation organisation Trekforce).

He is best known as a star of MTV's reality series The Osbournes (2003-05) along with his father Ozzy mother Sharon and sister Kelly. He was diagnosed with relapsing remitting multiple sclerosis in 2012.