The 45-year-old Bridget Jones actress was barely recognizable as she posed for photographers on the red carpet with her boyfriend, recording artist Doyle Bramhall II.
While nipping and tucking seems to come with the territory in Hollywood, Texas-born Zellweger looks like a different person, prompting a startled reaction from fans.
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Zellweger, who won an Oscar for her role in the 2003 civil war epic Cold Mountain, has been the centre of speculation over eating disorders and plastic surgery before.
"When you read reports that you are starving yourself or that you are anorexic, it’s very unfair and disappointing," she said in a 2013 interview with the U.K.'s Daily Express.
"It's not very pleasant to read reports which say you’ve gone too far or this or that."
A third Bridget Jones movie is said to be in development, with Zellweger expected to reprise the title role.