THE FAT BOYS make no claim to being gourmands. They're junk-food gluttons who have used their raps to boast about their ability to put away pizza and snarf down snacks. But what they put on their plates isn't half so troublesome as what goes on their records, for it seems that the Fat Boys are becoming junk rappers as well.

Take a spin through "The Fat Boys Are Back," and all you hear are cliches: "Yes, Yes, Y'all" grinds down one of Kurtis Blow's favorite phrases; "Rock-N-Roll" rehashes Run-D.M.C.'s "Rock Box"; and "Hard Core Reggae" is a drab dub derivative. Even the tubby trio's delivery, once so witty, has worn down to an annoying blare.

That's surprising, given the group's hammy charm in the film "Krush Groove," but, then, maybe that's just the difference between vinyl and celluloid. After all, the Fat Boys don't especially sparkle on the "Krush Groove" soundtrack, where their "All You Can Eat" is upstaged by Chaka Khan's "Can't Stop the Street," Kurtis Blow's "If I Ruled the World" and LL Cool J's "I Can't Live Without My Radio."

At least the Fat Boys' wide-screen debut made it into the theaters on time. "Good to Go," the go-go movie heavily hyped during its filming here in the District many months ago, continues to be held up by production delays. Fortunately, that hasn't stopped Trouble Funk from releasing its soundtrack single, "Still Smokin'." Matching the usual percussive power with sly harmonic tricks, it's a major step forward for the band most likely to make go-go go national.

Still, there are times when it seems as if Trouble Funk's big mistake is playing it smart. Consider the success of the Boogie Boys, a New York rap act whose best work is long on rhythm but short on subtlety. "A Fly Girl" is a typical example, being both "def" and dumb. But as they say, if the groove fits, work it.

THE FAT BOYS -- "The Fat Boys Are Back" (Sutra SUS1016); "Krush Groove" (Warner Bros. 25295-1);

BOOGIE BOYS -- "The City Life" (Capitol ST12409);

TROUBLE FUNK -- "Still Smokin' the Fat Boys, Trouble Funk, Boogie Boys, UTFO and the Real Roxanne, Little Benny and the Masters and the Junkyard Band, appearing Sunday at the Capital Centre.