Lionel Richie says the stress of his daughter's expanding career is most likely the reason for her shrinking dress size.

"I know what's happening with her right now, she's a nervous wreck," Richie says of Nicole, who was heavier when she co-starred with Paris Hilton on "The Simple Life."

"She's like her father, you can either blow up or you can shrink away," the R&B crooner told "Access Hollywood" in an interview. "And right now, she's just feeling a little bit of the pressures of her new business. So in this case ... she will be all right."

"Dad is on the case," he said.

The 24-year-old Richie has said she was always really thin, but went through a heavier stage during the first season of "The Simple Life."

In October, FOX announced that feuding ex-friends Richie and Hilton would not return for a fourth season. The network said its midseason schedule didn't have a time slot for the reality series.

Richie is engaged to Adam Goldstein, a professional club disc jockey who goes by DJ AM.

Her new novel, "The Truth About Diamonds," is described by ReganBooks as a "no-holds-barred look at Hollywood's new elite, behind the velvet ropes, inside star-studded premieres and parties."