London (AFP) - Usain Bolt's coaches have joked that he will develop "a belly" within two years of retirement, but he says he has no doubts about hanging up his running spikes.

Bolt, 30, will retire after the World Championships in London in August after a sensational career in which he has amassed eight Olympic gold medals, 11 world titles and three world records.

"Everybody wants me to continue, but it's not as simple as it is. I've done what I wanted to do. I've done great in the sport," the Jamaican star told the BBC in a television interview to be broadcast on Saturday.

"People just want to see more and more, but you as a person have to decide that this is it. I don't want to continue and then start losing, because I hate losing."

Though famously fond of the high life, Bolt says he does not intend to lose control of his waistline once he stops competing.

"I have a bet with my managers. They've given me two years before I get a belly," he said with a chuckle. "I can't let that happen."