Monica, Dieting for Dollars

And now it's time to see who won the office pool. Monica Lewinsky has officially signed on as a spokeswoman for the struggling diet company Jenny Craig Inc., and in announcing the deal yesterday, she revealed how much weight she has lost on the company's diet plan: 31 pounds!

It had been long rumored that Lewinsky was going to sign on with Jenny Craig, but that first she had to go on the diet and lose weight. A noticeably slimmer Lewinsky was in Maryland two weeks ago to testify at a pretrial motion hearing involving charges against her former friend Linda Tripp, igniting speculation as to just how much weight she had lost.

Lewinsky, 26, is starring in several Jenny Craig commercials. They will begin airing Sunday as part of a $7.2 million campaign to reverse Jenny Craig's profit shrinkage, which has forced the company to close 86 weight centers.

Tipper Gore Hospitalized . . .

Second lady Tipper Gore spent the night in Baltimore's Johns Hopkins Hospital after having a growth on her thyroid gland removed for analysis. The White House released a statement that said the growth was discovered during treatment for an exercise-related injury. Her husband, Vice President Al Gore, accompanied her to the hospital and planned to remain with her overnight.

Mrs. Gore's spokeswoman, Camille Johnston, told The Post that her boss "is not out of it yet, but she was in perfectly good spirits [yesterday] morning." She was expected to be released today.

. . . But Still Rockin'

On the brighter side of Tipper, the co-founder of the now-defunct Parents Music Resource Center has made her pop music recording debut. Gore plays drums on the new single by Diva Zappa, the 20-year-old daughter of Gore's onetime nemesis, the late Frank Zappa. The single, "When the Ball Drops," was released to radio stations yesterday. It was written by Diva Zappa's brother Dweezil, and also features Gore's daughter Kristin and pop music star Lisa Loeb.

Schulz Sends His Regrets

It looks as though Snoopy will not visit Washington for the new millennium. "Peanuts" creator Charles Schulz, 77, has declined an invitation from President Clinton to spend New Year's Eve at the White House, citing his chemotherapy treatment. Schulz's colon cancer was recently diagnosed, which led him to announce that he will discontinue the beloved comic strip.

End Notes

David Hasselhoff Syndrome? The head of Salomon Brothers' German operations, Daniel Lee, 50, is stepping down to become a country music star . . . Censors in Thailand have banned the Jodie Foster movie "Anna and the King," saying it's "inaccurate and insulting to the royal family." In other Jodie Foster news, the actress says she will not reprise her Oscar-winning role as Clarice Starling in an upcoming sequel to 1991's "The Silence of the Lambs" . . . Rap impresario Sean "Puffy" Combs insisted to reporters at a packed press conference yesterday that he is completely innocent and was not involved in a Monday morning shooting at a New York nightclub. Combs faces weapons charges.

Lloyd Grove is away. The Reliable Source will resume when he returns.