Apparently, not all of us are feeling the post-Christmas bloat. Certainly not Stephanie Seymour and Bar Refaeli, who are spending the holidays flaunting their curves in itty-bitty string bikinis.

Seymour showed off her still-fabulous-at-42 supermodel physique in a tiny white halter bikini as she relaxed with her family on the beach in St. Barths.

Meanwhile, model Bar Refaeli was snapped on vacation in Mexico with her curves on show in a teensy-weensy floral-printed string bikini. We're betting boyfriend Leonardo DiCaprio is pretty bummed that he's in L.A. and missing this sight.

And Rihanna -- still in Barbados -- swapped her feline-print one-piece for a skimpy, multi-colored, patterned bikini before hopping on a jet-ski.

Maybe it's time to keep that resolution of hitting the gym (at least once a month) in 2011?

Check out our gallery of more sexy stars in bikinis above.