To those who don't have breakfast,healthy is not vert important.TO引导的是什么从句

句子少了一个单词,应该是这样的：
To those who don't have breakfast,(being) healthy is not very important.
这是倒装句,原来句子是这个：
Being healthy is not very important to those who don't have breakfast.
我想,从这个句子你应该可以看出什么是主句和从句.