In contrast to most Washington parties, where thin is in, the guest of honor at a Capitol Hill bash last night was happy to be told, "You're getting fat."

"We call that insurance," replied Mitch Snyder, leader of the Community for Creative Non-Violence and erstwhile holder of a hunger strike. With the fate of his shelter for the homeless at stake in a struggle with the federal government, Snyder, who went 51 days without food in 1984, apparently never knows when he could use a few extra pounds.

He does, however, know when he could use a few extra dollars for CCNV, and that was what last night's gathering was all about. Donors paid $25 a person to visit the house owned by philanthropist Stewart Mott, and to sip wine, munch brie and kiwi fruit and meet Snyder and Dr. Benjamin Spock, the celebrated pediatrician and supporter of various causes.

Spock said his association with CCNV goes back to 1981. "Yes, we know them well," said Spock's wife, Mary Morgan. "We always get arrested together."

Spock and Morgan were part of a 1981 White House protest against budget cuts that landed the demonstrators in jail after a show of civil disobedience.

But last night, it was CCNV's current problem that was on their minds.

CCNV is battling in federal court to keep its shelter at Second and D streets NW open.

The federal government is seeking to shut it down and move the male residents to a shelter in Anacostia -- a move that Snyder charges is a stopgap measure that will force many of the homeless back to the streets.

"It will mean certain death for some of them," Snyder told Spock last night. Spock replied, "It's worse than crazy, it's evil."

Snyder, whose organization operates on a $250,000 annual budget funded by small donations, said he relies on "prayers to God" to keep the operation going. But last night the Lord got a little help from Spock, Morgan, Sargent Shriver and Rep. Charles B. Rangel (D-N.Y.) and his wife, who sponsored the fund-raiser. CCNV spokesman Carol Fennelly said they hoped to raise about $500 from the evening.

"I admire you very much for holding on," one guest told Snyder as she grasped his hand to say goodbye.

"We can't do anything else," said Snyder. "If we let go, our friends will die."