Portion control on unhealthy foods or Overload on Healthy Fo

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Through the years I've heard so many different things from trainers, nurtiontists etc about how to eat "right." Some say "eat what you wan't but in smaller portions" others say "eat healthy foods until you are full" and others say "too much of a good thing is a bad thing" I never really know which one is "right" or "better." I have done a little of both but what do you guys think? What works for you?

-Byrdie