Usain Bolt is confident of two things - he won't make a comeback and he's not doing to grow a belly once he exits athletics in August.

The eight-time Olympic champion will retire following the World Athletic Championships in London later this year, putting an end to an amazing career which began at the 2002 World Junior Championships.

Bolt has 11 World Championship gold medals to his name, completing the 100m, 200m and 100m relay treble at three world championships.

The 30-year-old has told the BBC that after London he's done and that you won't be seeing the Jamaican sprinter launching a comeback at any point.

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"I have a bet with my managers, they give me two years before I get a belly so I can't let that happen," Bolt said in a sneak preview of the BBC documentary, Usain Bolt: The Final Chapter.

"Everybody wants me to continue but it's not as simple as it is. For me, I've done what I want to do. I've done great in the sport. People just want to see me more and more but you as a person have to decide that this is it. I don't want to continue and then find I'm losing, because I hate losing."

Bolt said he's aware of great sportspeople damaging their reputations by mounting comebacks to their respective sports after reaching their peaks. The only blemish to his career was a false start disqualification in the 100m final at the 2011 World Championships final but Bolt said he has no regrets.

"There's no regrets. If you look at a lot of top athletes that's the one thing to use to damage their careers, just a little bit. By being so dominant throughout their career, retire then miss their sport and come back," Bolt said.

"I don't think my coach will coach me either," he added.