The prime minister wants Mr Motivator to help get the UK fitter
TV fitness guru Mr Motivator has met Gordon Brown, fresh from a morning run, at Downing Street.
The prime minister told Mr Motivator, real name Derrick Evans, morning was the best time to exercise, "as long as you can actually fit it in".
Mr Motivator, well known in the 1990s for his colourful leotards, is returning to GMTV to inspire fitness.
The PM, who was more formally dressed, joked: "I'll tell the cabinet ministers that you're after them."
Earlier this week, Mr Brown told the Observer on Sunday he wanted to be fitter and had taken up running - but admitted he would not get back to being "the sprinter that I used to be".
Greeting Mr Evans at Downing Street, Mr Brown said: "It's a joy to have you here - I've just broken from my run."
Last week the government launched its new strategy aimed at curbing obesity rates in England.
Mr Evans, who is launching his own campaign, says he is returning to GMTV because "waistlines have got bigger".
The prime minister said it was important to give people incentives to get fit.
Over Christmas he said he had set up treasure hunts for his children at the end of walks, to encourage them.
"I keep telling my children, five fruits, five vegetables a day. I think it's really important.
"And if you start very young, you do it continuously. But if you don't start young, it's sometimes difficult to persuade people to do it."
He said he wanted Mr Evans to help out with the government's new anti-obesity campaign Change4Life by encouraging people to take more exercise.
The prime minister told the TV fitness guru: "I would like you to go round the country and talk to them about how they can get motivated themselves."
And he joked that Mr Evans could help inspire the Cabinet to more action, saying: "I think you should come and motivate them."
Ministers have warned that, if left alone, obese and overweight people would cost the taxpayer in England £50bn by 2050.
A Foresight report, published last year, predicted that by 2050, 90% of today's children will be overweight or obese.