Know the Problem
You should have a realistic view of the problem, is it with you or the person who makes the fuss about eating anything to everything? It is possible that you may be forcing your child or any other person to eat something they do not like. Be adaptable instead of forcing people to eat what they do not like to eat.
It is possible that some people do not like one thing to eat in the morning but they can eat it willingly in the evening. So you can be a bit flexible with the routine and serve the food at the time your children or the fussy person likes to eat. Forcing them eat the same thing twice a day or even more can turn them off the food altogether.
You may also be forcing people to eat too much at a time, even greater than they can digest. Think of the quantity and reduce it to a level that the person prefers. Once they hook on the food you may increase the quantity gradually, if required.
Use some sort of motivation instead of stuffing the food in the mouths of children. Use the food which the person likes the most as an incentive to eat what they do not like but is essential as per the balanced diet requirement. The children can especially be motivated to eat such food if they see something like ice cream as an incentive.
Sometimes it is possible that a person refusing to eat food properly has some other problems, including some health issues. So it is better to get a counsellor's help instead of going with your choice straightaway. This can help them to be back on the proper diet.