Getting fit is no laughing matter for comedian Ricky Gervais.

The Office star looked in a whole world of pain as he attempted a workout in London's Hampstead Heath yesterday.

Sweat was dripping from the star's grimacing face as he power-walked around the park, his iPod in place to keep him motivated.

He's not having a laugh: Ricky Gervais works out in London's Hampstead Heath yesterday

He left his trademark 'slimming' black T-shirt at home in favour of a brown one emblazoned with the words 'Let's hug it out, bitch', a catchphrase from the US TV show Entourage.

Gervais, who now spends much of his time in Hollywood, has sported a rather hefty paunch in recent times, a sign the good life is starting to catch up with him.

Uphill battle: Ricky breaks out into a sweat during the walk

But his success has paid off in other ways.

Two shows he created garnered a total of 14 Emmy nominations in the US earlier this month.

The American version of 'The Office' is up for eight awards, including Outstanding Comedy Series while Extras: The Extra Special Series Finale is up for six coveted awards including two for Gervais himself.

Fit to burst: Ricky Gervais with his partner Jane Fallon in West Hollywood earlier this month