All this food talk is making me hungry...
Once again we see a huge cultural difference between the West and the East, particularly, Japan. Kids in Japan are strongly encouraged to eat everything, no "likes" or "dislikes" when it comes down to it. Actually, they may dislike something, but they are still expected to eat it. I was told by Japanese teachers that this is for their own good basically, to instill good eating practices and build an appreciation for nutrition. It also builds character and teaches children not to waste. Compare this to kids in the West. I can only speak from an American point of view, but the amount of waste is incredible. Children are served a full lunch, but eat what they want and throw out the rest. I'd say nearly half of the good goes in the garbage. Vegetable on the plate = FDA nutritional standards, but those items almost never get eaten. Lunchtime in the States is a social activity; more talking and playing goes on than eating. In Japan, classes, or the whole school, sit down and eat TOGETHER. Lunchtime is for eating. Sure, there is talking and socializing, but the focus is eating lunch, and finishing it.
I know a kid down the block, he's 11. He basically eats only white/brown food, meaning, chicken nuggets, fish sticks, chips, yogurt, applesauce, and french fries. He's eaten like this for years. He's creating an eating pattern that will shape how he eats for the rest of his life, just like a previous poster commented that their habits had been built from a young age. Is that healthy? What will this kid do when he goes somewhere that doesn't serve his "favorites"? Will he be willing to try something new and different when he's older? Probably not.
I like the concept behind "eat everything" in Japan. I like that they appreciate food and try not to waste. Americans, or Westerners, look like spoiled, greedy jerks; we have so much but we throw most of it away. As an ALT you are walking into their country, their culture, their rules. Choose your battles, but don't be so staunch about what you will or won't eat. Show a little flexibility. Otherwise, you'll be reinforcing the negative stereotypes of your home country, or the West in general. Yeah, they will accept you and allow you to eat carrot sticks and pb&j. They will smile. But in their heads or when you're not around, they will be talking about the "picky foreigner" who is selfish and unwilling to try anything.
Ki Ken Tai Ichi!