Rahul is an extremely fussy eater. He picks at his food for hours, and ignores his parents when they demand that he finish fast. Ultimately, after his mother has pleaded and threatened him for long, he finishes a meal, only to repeat the same process at the next mealtime. 
 

Punishment

In such cases, punishment does not work. Your child will believe that he is being treated unfairly, no matter what the situation. So if you slap your child or punish him in any other manner, resentment will build up and he will continue to behave in the same way. 
 

Psychological Reaction

Even though your child might realize that what he is doing is wrong, and that he is harming himself in the bargain, he will continue to behave in the same manner. Children have an inbuilt system that rebels authority, so punish your children to the minimum. 

If Rahul keeps playing with his food, the right thing for mother to do would be to simply pick up his plate after a reasonable time. He will, no doubt feel hungry in some time. So what does she say when he comes running to her after a couple of hours? 

Does mother give Rahul something to eat? The answer is NO. 

True, it seems horrifying for any mother to let her child stay hungry, but missing a meal now and then will not cause any harm at all. It will cause some discomfort at the most, but that is it. And when you think about it, it's far better this way than to slap your child or give him a yelling. Yelling may work when a situation requires immediate attention. If Rahul was misbehaving at a gathering he needs to be told in no uncertain terms that he better behave himself or else… But long-term solutions require subtle handling. 
 

But isn't denying your child food when he wants it, a punishment?

It all depends on the way you put it across to your child. Rahul has to be made to feel that it's all in his hands. Rahul's mother should not use words like 'Let this be a lesson to you.' What she should say, instead is, 'I'm very sorry that you have to go hungry Rahul, but now you will have to wait for another two hours before you can eat again.'
 

No arguments

At dinner, you can be sure Rahul will scrape every morsel off his plate! Of course, Rahul will not learn in one day. He will stick to his old habits for a while, but then he will slowly come around. All his mother has to do is make sure she quietly picks up his plate without any threats. She simply asks Rahul if he doesn't want any more food, because dinner will be laid only at 8:00.