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Jennifer Hudson's got some advice for her Weight Watchers successor, Jessica Simpson.

"Try not to snack with the baby," she told ABCNews.com Tuesday night at the New York launch of her QVC clothing line. Hudson became the diet company's spokesperson after giving birth to her son, David, in 2009.

"My baby likes making cakes," she said, "and when you're making a cake you always lick the stuff off your fingers. Those things, we don't realize what we're taking in."

"It helps if you write it down," she added. "Write down what you're eating, you'll be far more aware. And be active with the baby. Be active with them and you'll stay in shape. There's no workout like running around after a 2-year-old."

Hudson, 30, slimmed down from a size 16 to a size 6 in 2010 and continues to stick to the Weight Watchers diet. Simpson signed on to be the company's new spokesperson in May after giving birth to daughter Maxwell Drew Johnson.

"I think she will do awesome," Hudson said. "She's a pro. She knows what she's doing, for sure."

Hudson's svelte figure inspired her to start a clothing line that enhances a woman's curves while making her feel "comfortable and cute," she said. Her collection of form-fitting dresses, blousy tops and maxi skirts debuts on QVC in September.

"It's a whole new world for me, although I've always had a love for fashion," she said. "It's a tough industry."

Hudson, who shot to fame after her stunning turn on "American Idol" season four, plans to return to the studio this fall. She wants to "take a lot of time" with her third studio recording and focus on songwriting, but there's one cover that might also make an appearance on the album.

"I was actually just listening to this song called 'Let Him Fly' by the Dixie Chicks," she said. "That, I really want to cover."