He's not going to starve himself. The more attention you give it (trying to get him to try things) the more he'll resist.
I didn't have this problem with my ds, but I never tried to get him to try anything and if we were having something different (that he may not like or want to try) or something I knew he wasn't crazy about, I would always make sure I made one thing that he liked. If that's all he ate, fine.
I would have healthy snacks available (yogurt, fruit, peanut butter on celery, cheese, hard boiled eggs, etc.),
Don't worry about it. It's a common and typical behavior. It's a control thing, learning to speak for himself, and finding out what about the world he likes in the meantime.
The thing about food is that you do not want to make it a big deal. If you tell him to finish his plate, then he will not learn how to recognize that voice inside that says "full". As an adult, he will feel the need to eat what is in front of him, essentially eating too much because it is what is presented to him. For example, an average meal at a dinner out is more than half your day of callories. HALF! If you were actually served portion correct sizes, you'd be VERY surprised at how much excess you are eating.
If you tell him to eat it and he will get rewarded, then he is associating pleasing someone with eating food. Making you feel better. This translates into centering all activities around food, and dealing with emotions by eating. Break-up = Ice Cream. Promotion At Work = HUGE steak dinner.
If you tell him that you don't care if he eats, then food will hold no value...enter junk food. If I am hungry, I am going to eat what is easy....McDonald's. I am not going to cut up these healthy veggies that I have here, I am just going to go grab a 1200 callorie and 39 grams of fat double cheeseburger here. You want fries with that?
My son and I checked out books from the library talking about making good food choices. We talked about the food chart, eating five colors a day in fruits and veggies. I am talking to you as a parent of a four year old who would eat pancakes, pb&js, and waffles. THAT"S it. No meat, no veggies nothing. He was not even willing to try it.
We started out slow. I offer him choices for breakfast...giving him the power. If he chooses poor like candy, we talk about how that can be a bad choice and it's my job as his mommy to help him decide the right choice. We can have pancakes, we can have a waffle, we can have oatmeal. His choice. If he doesn't want those, he chooses not to eat. He's got to eat the good before he can treat himself to the bad.
Lunch I found out worked wonders if we sat down and ate together. Removed all other distractions, and even invited a friend over to eat with us. Again, choices. He may have PB&J, he may have mac n cheese, he may have fruit and yogurt. Good in to have LOTS of energy to go to the park and play! Good in to have LOTS of imagination while we do a craft. Good in to grow big and strong like Daddy!
Dinner was always a problem. We are still working on it. I am phasing him in. I started out making him a meal that I know he would like that I am okay with. I also would ask him if he wanted to try a "bonus food", a game. If he tried it, he did not have to eat it. He could spit it out if he didn't like it. As a reward for "trying something new" he got to have a "good choice stone". He gets stones when he makes a good choice in the day, and he looses them for making bad ones. He is rewarded with non-material items such as staying up an extra five minutes at the end of the day, getting another book at bedtime, inviting a friend over to play. He closes his eyes and opens his mouth (it's all about the look of food with some kids). Some times he spits it out, sometimes he likes it. We have discoverd he likes most veggies, and even have some meats in his normal rotation of dinner foods now. One night a week I don't give him a choice, he eats what we eat. I always make something really basic that is in the generality of what I know he will like, but it's his choice. He can eat what we eat, or he can not eat at all.
If he eats three good meals a day, which does not mean he has to finnish them, he may pick a treat out of the "green bag" which is where we put all of his candy from holidays.
We hit the jackpot this year...my four year old son said to me "make sure the easter bunny brings me some veg-e-tables so I have lots of energy to play. When I eat them, I can have the junk that he's going to leave me to!"
Don't fight this so hard. Offer delicious meals at dinner time, and if he wants something else he can get up and get cheese from the fridge and bring it to the table. Only those who eat the table food get dessert (which again is delicious - whatever he really likes eclairs or chocolate pie, whatever) and then relax and let it go. Don't act punitive, don't be tense, just let it go.
This must be miserable for him too to eat things that are unappetizing.
This is a phase he's going through to test his independence. He will eat when he gets hungry, and he will stop this behavior too -- in a few months:)