She is famous for her voluptuous figure, often outshining the ‘size zeroes’ on the red carpet with her killer curves.

But Scarlett Johansson was spotted in Malibu over the weekend looking more curvaceous than usual.

Which is perhaps why the actress was out pounding the pavement, working up a sweat with a jog alongside her new boyfriend Sean Penn.

Working up a sweat: Scarlett Johansson, displaying a fuller figure than usual hit the pavement in Malibu with boyfriend Sean Penn

Scarlett’s rounder stomach was noticeable under her tight exercise gear, a small bump protruding beneath her grey vest and black lycra leggings.

The 26-year-old went incognito in a cap and sunglasses, keeping her head down as she concentrated on her workout.

She stood out, though, in her bright pink Vibram FiveFinger sport shoe, designed to imitate barefoot running.

Sean, 50, was more casual in a T-shirt and jogging shorts and regular trainers.

Rounder figure: Scarlett, 26, was sporting a noticeably rounded stomach during the jog

The pair were joined for the jog near Penn’s Malibu home by friend Owen Wilson, who puffed away behind the couple in a long sleeve T-shirt and shorts – the boys soon powered ahead though, leaving Scarlett trailing behind in their wake.

The He’s Just Not That Into You star’s rounded stomach has led to some internet speculation that she might even be pregnant, although it could just be down to some unforgiving tight clothes and a big lunch.

A pregnancy would come as just as much of a surprise as the couple’s romance – the pair, who have a 24-year age gap, were first linked together back in January, just weeks after she announced her divorce from her husband of two years, actor Ryan Reynolds.

Three’s company: Scarlett and Sean were joined by Owen Wilson for the workout session

They have been snapped together a couple of times, including last weekend at Reese Witherspoon’s wedding.

The are said to have met at the Chateau Marmont in West Hollywood while Scarlett was filming We Bought A Zoo, her new movie alongside Matt Damon.

But Scarlett’s representative has denied any romance saying the pair have been ‘friends for years’ – despite recent pictures of the pair at lunch where Scarlett placed her feet in Penn’s lap.

Voluptuous: Scarlett is known for her killer curves but was looking far more svelte in February at the Oscars

And Sean’s ex-girlfriend Jessica White appeared to confirm the relationship in a recent interview.

‘I think Sean needs a good woman in his life,’ Jessica told entertainment website Popeater.com. ‘They’re great together.’

Owen, Sean and Scarlett are all friends of director Woody Allen’s, though it is unclear if it was he who introduced them.

Scarlett is a muse to Allen and starred in three of his films, Match Point, Scoop and Vicky Christina Barcelona, while Owen stars in his latest, Midnight In Paris.

Wait for me! Owen and Sean powered ahead, leaving Scarlett (in background) far behind

Penn’s relationship with Woody goes back to 1999, when he starred in Sweet And Lowdown. He will next be seen in The Tree Of Life with Brad Pitt.

His film Fair Game, with Naomi Watts – inspired by the real life events of CIA operative Valerie Plame who discovered her identity had allegedly been leaked by the government as payback for an op-ed article her husband (played by Penn) wrote criticising the Bush administration – was released in the UK last month.