A child can no more control his or her size than they can control their height or hair color or gender or sexual preference.  It’s also true that children are born knowing how  to eat.  They know what they want to eat and they know how much to eat.  Too often, well meaning parents step in and interfere with that natural process which can lead to years of disordered eating if not full blown eating disorders. If your child seems like they are eating more than they "should" or that their body is bigger than you think it "should" be, if their size has always been consistent on their growth chart, it's time to check your assumptions.  Who says how a big a person is supposed to be? I believe there is a myth among parents that left to their own devices, kids will eat and eat and eat.  That is simply not true.  The body is a biological machine and when kids are taught to listen to it's cues, they will eat the amount of food that is right for their bodies.  That amount might be more or less than a predetermined amount that you think is appropriate.  It might be more or less than the serving sizes on a box.  It might be more or less during a given meal, a given day or a given week depending on how the child is growing and what his/her nutritional needs are for the time period.  It is not up to you.