It's not fair

My daughter says it's not fair that her friend can "eat whatever she wants" without gaining weight.
I have my theories on that. Nothing based in fact. They're just theories.
For one thing, once you get fat it seems like it's way easier to get fatter. One cookie here, one slice of pizza there and voila, you've gained five pounds. Or so it seems.
Maybe the person who seems to be a bottomless pit is really not eating all that much. Perhaps she is only eating large quantities-or what seem like large quantities-occasionally but eats sparingly the rest of the time. That would mean that her overall intake is moderate.
I think most people forget that it's not each meal but intake for the day, week, month, over a lifetime that determines your weight. So just because some one chows down on pizza, coke and chicken wings (yum) once in a while doesn't mean she'll end up roly poly. You've got to secretly spy on her during the rest of the day. She's probably eating fat free sugar free yogurt and drinking water.
Lastly, the chances are if she's really eating the same way you are-that is, with abandon-she's probably going to get fat. It just hasn't caught up with her yet!
There is justice in the world, I hope. Otherwise, it's not fair!