I spend a lot of time at our children's centre and used to be a nursery nurse. Trust me, ALL toddlers do this. Mine included. It's how you behave and react that matters. Cook one dinner, thats it take it or leave it. Act like you really don't care wether he eats it or not. Ive know a few parents who cook one thing, DC says no, then they cook something else, DC says no again....all this just gives DC power and attention -rewarding him for not eating because the parent doesn't have the balls to just say NO!
DS was a pain for eating and snacking so we now have the following routine:
Breakfast
fruit snack
lunch
savoury snack
dinner
(he can have whatever he likes for pudding if he has eaten nicely during the day).
This is stuck too, but he does have some control. I will ask him which of 2 meals he would prefer so he feels he has a choice. He likes to help cook it aswell.
We aim to eat at the table, as a family for at least one meal a day.
I praise DC for his behaviour while eating (using a knife and fork, please and thankyous) rather than drawing attention to how much he has actually eaten.
A healthy child will never starve themselves. DC went on hunger strike when I first started this routine. It lasted one or two days, he lost no weight. He got the messege very clearly. Toddlers can survive on very little food. Persiverence is the key.
A time limit is also a good idea mumsobusy
If your worried you could go to your GP/HV. If he's loosing weight I would. You could also give vitamins for a while, for a little boost while he is going through this phase.