Keeping herself trim could all be in vein for Angelina Jolie.

The 32-year-old actress, whose figure seems to be shrinking, is known for her dedication to exercise.

But there were fears she may have taken her regime too far as she sported a prominent vein on her forehead.

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Facing up to her figure: Angelina Jolie at the premiere

Broad smiles: With boyfriend Brad Pitt in New York

A tell-tale sign of extreme weight loss and over-exercise, pulsing blue veins have also popped up on her arms, hands and wrists.

As Miss Jolie and boyfriend Brad Pitt arrived for the New York premiere of her movie A Mighty Heart, she smiled broadly. But that was certainly the only broad thing about her.

According to health and fitness experts, such prominent veins are usually a sign of physical over-exertion.

"Such increased vascularity is often the result of over-exercising, particularly weight-bearing or resistance work," said Mark Munroe, a trainer based in Kensington.

"If Angelina is pushing herself too hard – and not consuming enough calories – then the body has to work harder to pump nutrients around which shows up in the form of bulging veins."

Last night, Miss Jolie attributed her weight loss to the death of her mother from cancer in January.

"Someone saying to me that I'm thin is not a compliment," she said.

"I've always been lean and this year I lost my mom and I've gone through a lot.

"I have four kids and I finished breastfeeding – it's been hard to get my nutrition back on track."

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Angelina with Marianne Pearl whom she portrays in her latest movie, 'A Mighty Heart'

The actress insisted observers were wrong to include her in the size zero trend.

"Instead of people saying I look like a person dealing with something emotionally, they assume it's because I want to fit into skinny jeans."

Miss Jolie has not ruled out new additions to the family. On US programme the Daily Show, when host Jon Stewart asked Jolie how many more children she planned to adopt, Jolie replied: "It fluctuates between seven and 13 or 14."

As the audience and Jolie laughed, Stewart said, "Wow, I'll tell you this: I admire that, because two is kicking my a**."

To which Jolie quipped: "Yeah, I understand that. Four is kind of kicking our a**, but we kind of feel like, 'Damn it, we're up for the challenge!'"

And she revealed that she and boyfriend Brad Pitt are helping to support other disadvantaged children.

"There are certain kids on the periphery that we want to help through school, whose lives we are starting to be involved in as well," she said.

"In our home it is all about how much we balance making sure that everybody has individual time, and right now four of them have very special individual time. We never want to have so many kids that we can't do that."

Jolie's latest film is A Mighty Heart, in which she plays the widow of murdered Wall Street Journal reporter Daniel Pearl.

Stewart asked Jolie about the story that claimed journalists schedule to interview her had been asked to sign a contract requiring that they not ask about her personal life.

Jolie confirmed "there was a memo" and explained it was from a representative trying to be protective of her.

She agreed: "It was excessive and I wouldn't have put it out there."

In one scene she is shown giving birth - and had to ask director Michael Winterbottom for advice because her own daughter, Shiloh, was delivered by Caesarean section.

"Michael had to try to explain labour to me because he was with his wife when she had children," Jolie revealed.

"It was very funny having a bunch of men explaining how to scream at the top of my lungs in a quiet floor of a real hospital in India. We were all screaming back and forth at each other - it was bizarre."