media_removed_toofab 102011

Mariah Carey
isn't shy about her curves -- putting them on display in a form-fitting black gown last night that really showed off her post-baby weight loss.

The 41-year-old mother of twins performed at one of four Escape to Total Rewards concerts held last night around the U.S.

Mariah, accompanied by husband and babydaddy Nick Cannon, stepped on stage at the New York show held at Gotham Hall -- where her hip-hugging mermaid gown accentuated her 70lb weight loss since having kids in 2011.

Carey wasn't the only performer of the evening: Diddy also played at Gotham Hall, Maroon 5 and Sara Bareilles played in Chicago, Cee Lo Green and Lil Wayne hit the stage in L.A. and Gavin DeGraw performed in New Orleans.

Celeb guests at the four events included a slim Mel B, pregnant Kourtney Kardashan, "90210" star Shenae Grimes, new "Dancing with the Stars" contestant Maria Menounos, a solo Ashlee Simpson and Rosie O'Donnell with fiancee Michelle Rounds.

Check out all the photos above!

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