Janet Luna and three people identified as her guardians were named in a lawsuit filed Thursday in Los Angeles Superior Court. The lawsuit alleges deceptive business practices and a violation of California's unfair competition law.
They are asking for unspecified damages, restitution and an injunction preventing Smith and New Jersey-based TrimSpa, maker of TrimSpa X32, from making claims that users of the pills can lose substantial amounts of weight.
Smith, 39, has endorsed TrimSpa and is a spokeswoman.
A message left early Tuesday with Joseph Farzam, an attorney for the plaintiff, wasn't immediately returned.
Ron Rale, Smith's lawyer, said Smith hadn't seen the lawsuit.
"This is news to us," he said, adding that "I'm sure to be speaking to her about it."
Last month, the Federal Trade Commission announced TrimSpa would pay $1.5 million to settle allegations that the company's weight-loss claims were unsubstantiated.
TrimSpa released a statement following the announcement saying it supported actions to clean up the weight-loss industry, but disputed the federal agency's allegation that a handful of TrimSpa advertisements that ran in 2003 and 2004 had insufficient substantiation.
TrimSpa also disagreed with any inference that its X32 product has no scientific support.