AS the hot young star of FOX’s hit teen drama “The O.C.,” Mischa Barton once had the world at her feet – but now she’s packed on so much weight friends fear she’s all washed up at age 27!

The former model used to be one of Hollywood’s sizzling it-girls. Then “The O.C.” was canceled in 2007, and her career nosedived. She was also busted on DUI charges and reportedly entered rehab.

ON APRIL 8, Mischa shocked fans when she stepped out in Los Angeles in ultra-short Daisy Dukes that highlighted her ballooning hips and extra pounds.

“Mischa’s friends are terrified she’s using food to cope with her problems,” revealed a close source. “She went from being one of Hollywood’s hottest actresses to a relative nobody, and it has taken an extreme toll on her confidence.”

To make matters even worse, the source says the “Sixth Sense” actress is strapped for cash and is stuck with a costly eight-bedroom house.

 She purchased the 7,607-square-foot white elephant in 2005 during the height of her fame and the real estate boom, and she unsuccessfully tried to unload it in 2010 and 2011. Now, she’s desperately trying to rent it out, but she’s had no luck because she’s asking a staggering $27,000 a month.

Despite her setbacks, the actress remains determined to jump-start her career, but so far she’s had limited success.

She’s in two films this year – “A Resurrection” and “Bhopal: A Prayer for Rain” – but neither is expected to do much for her career. She’s also slated to star in a British film.

Mischa has also tried her hand in the business world, opening a London boutique. But she hasn’t found any luck with that venture as insiders say her overpriced items have failed to catch on.