Juice fasts are a hot topic these days. Beyonce famously used the Master Cleanse to drop 20 pounds for “Dreamgirls” (For those not in the know, the Master Cleanse consists of water, cayenne pepper, and maple syrup for 14 days — no food.) “It was tough; everyone was eating and I was dying,” said Beyonce. (And Beyonce isn’t the only one to get onboard this trend. Gwyneth Paltrow and Naomi Watts love Organic Avenue juices.)

Before you start juicing, keep in mind that not all juices are healthy or safe. “Juicing is a great way to get nutrients into your body — but drink green juices,” says Lipman. “A lot of the [other] juices are too sugary.” Fruit juices can actually cause you to gain weight, and it doesn’t take a rocket scientist to know that the Master Cleanse isn’t exactly safe (a.k.a. devoid of almost all nutrients).