David Cameron has revealed his secret to keeping fit in mind and body as Prime Minister - get an early night and delegate a lot of work to your team.
Mr Cameron said he tried to have a run and a game of tennis every week, but admitted he did not always manage to fit them in.
And he said a prime minister would be "hopeless" if he or she allowed themselves to become "exhausted and fried mentally" by overwork.
The PM's approach contrasts markedly with the regime followed by Margaret Thatcher, who famously said she slept as little as four hours a night during her time at 10 Downing Street.
During a question and answer session with workers at Unilever's headquarters in Mumbai, India, Mr Cameron was asked how he kept fit, given the pressures of his job.
He replied: "In terms of how I try to keep body and soul together, I try to stay a little bit fit.
"So I try to go for a run a week, I try to play a game of tennis every week and I try not to go to bed too late.
"Like all these things, that doesn't always work, but the most important thing is to have a very good team around you to make sure you can delegate and have a team you can work with and get things done for you."
He added: "If you are exhausted and if you are fried mentally, you will be a hopeless prime minister.
"You have to try to keep a good equilibrium and balance and then hopefully you can make good decisions."