# Is this really the kind of fast that I would want ... under himself?

"This is not the kind of fast I want ... under himself." 

# A day for anybody to humble himself, for him to bow down his head like a reed

This means the person is bowing down, but he is not truly humble. "A reed" represents a weak plant that bends easily. 

# Do you really call this a fast, a day that pleases Yahweh?

"Surely you do not think this kind of fast pleases me!"