Why does the fat girl's hair curl?

A man asked a child, why is your hair so curly? The child said that when my mother was pregnant with me, she drank boiled water every day.

Not every fat girl has curly hair, but her personal constitution is different. Some naturally curl at birth, some slowly curl when they are long, and some begin to curl at puberty. This is uncertain. It doesn't matter whether she is fat or not.

I 1.6, 130 kg, relatively fat, but my hair is not curly.