Slenderize This!

7/30/2007 5:34 PM PDT

Slenderize This!

Oh yeah, Posh Spice needs to be a little slimmer. Uh huh.

Last week's "Welcome to L.A." party for Becks and Posh featured Fuze's Slenderize drink -- in six fruit flavors that have five to ten calories per serving -- and already slim stars like pop blonde Jessica Simpson and tiny-waisted teen Hayden Panettiere are downing the diet beverage by the case.

Robowife Katie Holmes requested the low-carb drink be available at the party -- though, really, do these svelte celebs need to be any skinnier?!