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The Duets" star has spoken out against Hollywood's thin ideal for years, but boyfriend Brandon Blackstock inspired her to shape up. "No one likes to be not toned when you are dating someone," said Clarkson, who flaunts a slimmer shape thanks to diet, cardio and strength training. "I'm eating better and working out, but I've always fluctuated within 20 lbs." Still, the singer stands by her curves: "I have no desire to be super-skinny."