The only advice that I can give is that it will pass. We went through this with both of ours (boys) at about the same age, now a couple years on and all is o/k. One thing that I think did help was introducing them to cooking, we bought them children's cook books and encouraged them to cook once a week each, it made them experiment and vastly improved their food choices. They made things some evenings that they could put in their lunch.
Regards Skipy.