My theory is to not make a big deal out of things.
E.g say absolute no to choc ever, thats what they are gonna want.
I have always been laid back about what dd eats, we have three healthy meals a day, if she chooses to only eat the potato at one mealtime thats fine. I don't force anything upon her. Pudding is normally fruit or yogurt so i don't take that away as punishment.
DD will normally eat veg/potato/pasta/rice but is not a big meat eater, occasionally tries a mouthful .
For snacks in between mealtimes she will sometimes ask for crisps/choc which i allow in controlled portions, other days she will ask for fruit or slice of bread which i also allow.
So there is choice for dd, but obviously i ensure the food i'm providing is majority healthy. Over the course of a week i know she is getting a healthy balanced diet.
This could either prove my theory right/ or it just means i have a good eater and next time round i may not be so lucky!
I think what i'm saying is if i had a child who refused to eat food fullstop, i would not have any junk on offer, so that the small amounts they did eat would always be healthy! But still i wouldn'd force feed or bribe.