How does Beyonce manage to keep fit? According to the gossip column Page Six in the NY Post, she utilizes the Def Jam detox.
...But pals of the tight-lipped newlyweds say the songbird is expecting the couple's first child. "She has gained a lot of pregnancy weight," a source said. "When she gains weight, she normally does the Def Jam detox, but not now." A rep for Beyoncé said, "I don't know if she's pregnant. Let me perform an ultrasound and get back to you." [NY Post]
I've done some research (i.e. Googling) to find out what exactly the Def Jam Detox or Def Jam Diet is, but haven't found anything legit on it. It seems to be something like the Master Cleanse, but again I'm not certain.