Nicole Richie has checked into a treatment facility to find out why she is unable to put on weight, the star's publicist has confirmed.
"Nicole Richie has decided to undergo diagnostic treatment to determine why she's not been putting on any weight," said spokeswoman Nicole Perna in a statement yesterday.
Perna added that the daughter of singer Lionel Richie was "working with a team of doctors and specialists whose focus is nutrition".
But the star's publicist stressed that her client was not being treated for an eating disorder.
"It is important to Nicole that she achieves this goal in a healthy way as this is not a treatment for an eating disorder," said Perna, commenting on the Hollywood socialite's desire to gain weight.
Despite denials of an eating disorder from the Richie camp, news of the star's treatment is likely to prompt further press speculation about her health.
The 25-year-old star recently admitted to Vanity Fair magazine: "I know I'm too thin right now. I'm not happy with the way I look."
But tiny Richie has vociferously denied media reports that she is suffering from an eating disorder, posting a statement on her MySpace web page last month insisting that contrary to "false accusations" made by CNN she had not checked herself into rehab because of one.
"I don't know why or how this rumour started, but I am home, in LA, and very happy. I do not have an eating disorder, and I don't know how many times I have to say it," the star ranted.
Meanwhile, it has been revealed that filming on the latest series of the Simple Life has been temporarily put on hold while Richie seeks the treatment her reps have confirmed she will undergo.
The news comes just a couple of weeks after it was revealed that Richie and her co-star in the reality series, heiress Paris Hilton, have ended a long-term feud. The pair were spotted dining together at a West Hollywood restaurant earlier this month.