J. -
My boss's daughter has done a lot of research on this problem (it's her job!) and here is the advice she offered recently:
"The parent's job is to buy, prepare, and put a variety of healthy foods on the table as well as to provide a pleasant eating environment. After that their job is done.
The child is responsible for how much they eat and even whether or not they eat.
If the parent follows this, the battle of mealtime is done and the child gets no attention for being a picky eater. It is important also to keep conversation positive, for example focused on family daily events, and not talking to the child about how much, what, or whether they are eating or trying to coerce them into eating By putting it on the table and modeling healthy eating habits the child will learn that "this is what we do during mealtime". If and when they are hungry, they will eat.
Two additional tips. The first is that when you think of nutrition with toddlers and preschoolers, especially, think in terms of weekly, not daily, servings of certain food groups- a nutritionally balanced week, not day!
Another tip is do not get hung-up on the scale at the doctor's office. If the child is developing normally and has the strength for all of the activities they want to do, they are eating enough!"
Hope this helps!
S.