After making Jessica Simpson's breakfast smoothie, I didn't think it was possible for trainer Harley Pasternack to top himself, but then I tried his PB&J smoothie, which counts Katy Perry as a huge fan. After tasting it, I found it hard to believe that it was good for me — it had all the nostalgia of a peanut butter and jelly on white bread: creamy and sweet, feeling more like dessert than a proper meal. But consider this — it contains an entire day's worth of fiber, is low in fat, and has high levels of potassium and vitamins B and C. It's also found a snug place in my ongoing smoothie rotation.