"A dress shouldn't look like a coat hanger," continues Lopez, who donned a skin-tight catsuit to perform on New Year's Eve. "Skinny girls miss out."
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Lopez -- who welcomed twins Max and Emme in 2008 -- says she's incorporated boxing into her routine ever since starring in 1998's "Out of Sight." The cardio aspect satisfies her "wild side." (Jessica Simpson has also picked up the sport.)
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Lopez also hits the StairMaster, and does a little "light training and cardio... biking, weight machines and lunges to keep those thigh muscles firm," she explains.