You're overeating after exercise
Just because you got in a major sweat sesh doesn't mean that slice (or two, or three) of pizza doesn't count. Even something you *think* is healthy - like a protein shake - can be adding hundreds of calories you don't actually need. In order to lose weight, you must be in a calorie deficit, which means you're burning more than you're taking in. The best thing to eat after a workout? An actual (healthy) meal.
[Photo via @romeestrijd]