Here's an excellent example of how much more you can eat if you're eating anything remotely decent.
Here is my lunch for today, a total of 610 calories. We have a tuna sandwich with light mayonnaise, an apple, an orange and 2 Dannon Light and Fit yogurts.
Now, here we have one single fast food menu item, the "McSkillet Burrito with Sausage" from McDonald's, also 610 calories. What is going to fill you up more?