I have never really read any of WL's diet topics, so sorry if I say the obvious:
Even if 1 calorie is 1 calorie, and let's say you follow a 1500 kcal diet (150g carbs, 200g protein, low fat), in terms of hunger it seems to be more satisfying to eat 200g rice + lots of chicken/fish etc per day than eating 1 Big Mac in the morning, and eating another in the evening...