If you've picked Fat Smash or Eat To Live Or South Beach as your "diet", the thing that is SO important to having a "back up" diet like Weight Watchers or counting calories is because sometimes you just don't feel like eating vegetables or eating anything that resembles "healthy". You know you should, but you just don't. All the positive self -talk and all that you do to avoid eating pasta or pizza or a cheeseburger just isn't going to happen. You just don't care. Your mind goes on automatic pilot and you head straight for the nearest comfort food. And unfortunately, sometimes you stay there for DAYS. One choice after another becomes pizza, more white bread, dessert and so on.
Until you get back to your Fat Smash Diet regimen, or Eat to Live or South Beach, or whatever you've chosen, you have to have a way to "portion control" the really bad trajectory of crazy comfort foods because the reality is, it happens to everyone. If you have a "back up" diet and you're incorporating diet fusion for those days that no matter what anyone says, you're not going to pick the salad, you're just hungry for white bread and you're going to have it, you'll be able to monitor yourself and frame the "bad days" with a semblance of control.
If you count Weight Watchers Points, you know that 2 slices of pizza is 12 points, and if you have a white bread sandwich at dinner, you'll count the points again. If you have some method -whether it's points or calorie counting or whatever -to be able to hold yourself accountable, you will not eradicate all the effort you put into the Fat Smash or other plant based/vegetable diet you did. And when you "come to", when you get back on the more nutrient dense road, you won't have an extra 10 pounds to fight. This is why you have to have a "portion control" back up plan.