(Photo: Gabriel Grams / Retna)

Jennifer Hudson continued her work as a Weight Watchers spokeswoman by attending the organization’s 3rd annual Walk-It challenge in Chicago. Looking trim in a purple WW baby tee and light grey skinny jeans, J-Hud showed local students how to stretch, bend and dance their way to a healthier lifestyle. The singer literally worked up a sweat as she demonstrated various movements and discussed how to successfully change your diet.

Hudson says the secret behind her 80-pound weight loss wasn’t really a secret at all. She simply walked for 30 minutes four days a week. She also quickly dismissed the notion that she lost the weight too fast. Speaking to the New York-based Pix Morning News show, she said, “I hear a lot of people say, 'Oh God, it was so fast' and I say, 'No, you do the math by the baby,'" referring to the two year time frame after giving birth to son David in 2009.

The star also emphasized that exercise should be fun. "Who wants to work out and not enjoy it?" she asked. "That's how I've been able to maintain the weight loss."