DD often went through stages where she wouldn't eat... used to worry my mum silly but not me.. My GP told me that a two year old does not have the mental capacity to starve themselves intentionally and as long as they weren't listless and loosing weight rapidly then it wasn't anything to worry about.
I was told to give Tia lots and lots of milk (either plain or chocolate) and to make it full fat milk. Tia was lactose intolerant so I used the soya milk with load of nesquick and well that went down really well...
As long as they are drinking then that is the most important thing.
Also I was advised to give her choices at her meals (just between two options) because two year olds tend to start wanting to take control. So the option meant that they thought they were taking control of the situation. Also never to make the meal the issue, food went down for a set amount of time if it went uneaten it was taken away. Nothing else was offered afterwards like sweets or crisps and no comments were made.
After a few months of eating barely nothing, all of a sudden she would eat like a horse for a few weeks then go back to eating nothing at all... You get used to it after a while...
She's a really healthy 8 year old now, she eats her meals (not everything all the time, but she sits down and eats something and again during growth times, she eats everything and then some)...Now she's at an age where she's more picky... but she's old enough to make those distinctions now... Apparently she's "allergic" to onions..
Take heart your LO is not the only one, and the more he sees other people (either kids or yourselves) eating the more likely he is to join in with eating.
Oh and what redshoes says about forcing your LO's do ANYTHING is never well received.. well there was never a truer word said.. the more you try and force them, the more they will resist... if they think you don't care... then they will just get on with it.