Painfully thin Renee Zellweger continues her disappearing act

Stepping out at a concert in New York, Renee Zellweger showed the dramatic effect a strict diet and gruelling daily workout can have on your physique.

The 38-year-old famously gained two stones to play Bridget Jones in 2001 - and fans at the time celebrated the fuller-figure look.

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The famished look: Miss Zellweger's matchstick figure shocked some fans (left), The fuller look: Renee in 2003

But the Oscar-winning actress's appearance at the Tom Petty and The Heartbreakers concert left some onlookers surprised at how much weight she has lost.

She showed off her slimline figure in a loose-fitting knee-length smock dress.

"It's almost as if she's wasting away," said one concertgoer.

"Her legs and arms were incredibly thin. Perhaps she's simply been overdoing the gym workouts."

For her role in Bridget Jones's Diary and the sequel The Edge of Reason, Miss Zellweger deliberately piled on the pounds by gorging on pizza, doughnuts and beer.

At the time, she said: "One doughnut does not do a thing. You've got to eat 20 a day for at least five weeks to get results."

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From curvy to waif-like: Renee gamely gained 2 stone to play eponymous movie heroine Bridget Jones, but since then her weight loss has been dramatic

But within weeks of filming finishing, she was pictured showing off a size-zero figure.

Although she remains tight-lipped on the subject of her weight, she is said to follow a microbiotic diet of lean fish, rice and vegetables.

Added to this, she endures gruelling two-hour daily workouts with a personal trainer.

The famously private star refuses to be drawn on her dietary habits.

"It saddens me every day when people come up and say, 'OK, how did you lose that weight?'," Renee said after playing the eponymous Ms Jones the first time round.

"I can't speak about it because I am not an authority on weight loss. I am just not.

"I am not challenged with a medical situation that's weight-related and that I need to pay attention to".

Before leaving the concert Miss Zellweger was seen chatting intimately with Sir Paul McCartney.

She smiled fondly at Sir Paul, 65, as they chatted at the venue in New York.