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ABC News' Sabrina Parise and Jennifer Pereira report:

Pop-R&B superstar Beyonce works hard at what she does. Three months after she gave birth to her daughter, Blue Ivy, she had a show scheduled, so she had to drop the extra weight.

In an interview with Shape magazine, the star who was born Beyonce Knowles said she gained 57 pounds during her pregnancy.

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Describing herself as someone who is "not naturally very thin," she added that she has to work to keep her body in shape. She told the magazine that 80 percent of her post-baby weight loss resulted from cutting back on food.

"I ate a very low-calorie diet. I stayed away from red meat and ate a lot of fish, replaced pasta and rice with quinoa," Beyonce said.

The Grammy Award-winning singer gave birth to Blue Ivy, her daughter with rapper-husband Jay-Z, Jan. 8, 2012, at Lenox Hill Hospital in New York City.

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Beyonce, 31, also told the magazine that she was at her ideal weight while working on her iconic "Crazy in Love" music video, saying that's the body size she aims for when she wants to get in shape.

"For me, dancing is what keeps me active and I would just say, everyone is not supposed to be the same. Be healthy and take care of yourself, but be happy with the beautiful things that make you you," she added.

She also said that she doesn't count calories.

"I always have breakfast, say, scrambled egg whites, a vegetable smoothie, or whole-grain cereal with low-fat milk. For lunch and dinner, I eat a lot of fish and vegetables. And throughout the day, I try to stay hydrated," she said.

But she does splurge from time to time.

"I always treat myself to one meal on Sundays when I can have whatever I want," she said. "Usually it's pizza, which is my favorite indulgence."

Beyonce kicks off her Mrs. Carter Show World tour next month, and tells Shape that once the tour wraps, she'll start trying for more children.

The singer debuted her new single, "Bow Down/I Been On," on her website Sunday along with a photo of a young Beyonce standing in front of a mantle full of trophies.

Check out her new song here: