"I know I'm too thin right now, so I wouldn't want any young girl looking at me and saying, 'That's what I want to look like,' " the 24-year-old "Simple Life" star tells the magazine in its June issue, on newsstands Tuesday.
"I do know that they will, which is another reason I really do need to do something about it," she says. "I'm not happy with the way I look right now."
The 5-foot-1 Richie was visibly heavier in 2003 when she began filming TV's "The Simple Life," which features Richie and ex-friend Paris Hilton thrown into normal jobs and responsibilities.
Richie, who has said she gained weight during a stint in rehab for heroin addiction, says she doesn't know how much she weighs today.
However, she says her eating habits are far from healthy: "I eat the worst foods — salty cheese-and-grease kind of stuff."
Stress causes her to lose her appetite, she says, and her split in December from ex-fiancé Adam Goldstein, a professional club DJ who goes by the name DJ AM, didn't help matters. "I had a bad breakup, and it eats me up inside when I'm upset about something," says Richie, who is dating Goldstein again.
"I get really stressed out, and I do lose my appetite, but I do force myself to eat. I tried to put the weight on my way, eating burritos, but that wasn't working, so I started seeing a nutritionist and a doctor," Richie tells the magazine.
Dr. Jeffery Wilkins, vice-chair of the department of psychiatry at Cedars-Sinai Medical Center in Los Angeles, who treats Richie, says doctors are "working on a systematic plan to get more calories in, and we're going to watch and see if it succeeds."
"If it's not anorexia, she should be able to gain the weight," he says. "If it ends up being anorexia, we'll help her with that."