Lewis Hamilton is chasing his fourth Formula 1 title, after losing out to Nico Rosberg in 2016

Three-time champion Lewis Hamilton has decided to race in Formula 1 this year without a personal trainer.

It is usual for grand prix drivers to employ a trainer to ensure they are in peak physical fitness.

But the Briton said he chose to take over his own programme this year as "a kind of challenge" he has set himself.

"Can you have the motivation to do it yourself and get ready and tone up, not having a trainer and be ready? I have," the Mercedes driver said.

The 32-year-old added that he had upped his physical preparations to match the greater demands of this year's faster cars.

"Every year you try to improve, but I would say I have taken a good step," Hamilton said after the Australian Grand Prix at the weekend.

"My discipline has definitely gone up in terms of my training and how specific I am with my diet."

Hamilton finished second behind Sebastian Vettel in the 2017 opener in Melbourne

But he denied he had significantly changed his approach to F1 in terms of the amount of commitment he put in over the winter after losing out on the title to former team-mate Nico Rosberg last year.

"I don't think so," he said after finishing second to Ferrari's Sebastian Vettel in Melbourne on Sunday, adding that his hectic lifestyle of global travel was not a hindrance to his job.

"I work hard every year and I have been touring. I have not been home much. I have been enjoying myself.

"It appears people judge off things they see and in previous years I arrived at the first race just as fit. I always arrive fit and ready. None of those things I do are a distraction. I have done just as much this year; it is just I have a job to do. I have made sure the fitness levels are higher than before so for sure I have applied myself better."

And he said his desire to win the title was even bigger this season.

"I had fantastic fight the past few years and last year was the closest I've had," he said. "But of course I want to win the world championship more than ever before.

"The hunger… while last year [I felt] the hunger couldn't be any more, it has freakin' doubled. So I am fit and ready.

"I am going home, for example, after this. Usually I stay out in Asia [before the next race in China] but I am going home to get my head down, rest and make sure I come back fighting for the next race because I believe I can win."