I agree with Tan, doing a bigger meal for lunch and not worrying so much about dinner. My DS (who is two) does exactly what your son does and it makes me want to pull out my hair! I especially hate throwing plates of food away! Grrr! So I try and give him more at lunch including vegies etc and it works some days and others it doesn't, but I think it is an improvement. HTH toddlers can be so frustrating!