Why people like slim girl/women?

From my previous discussion, about a beautiful girl, most of the people said, they like slim girl/women. Most of the people don't like fat girl or women. Fat girls also know this. They were very in tense, they first aim in life to weightless. Because they know people like slim girls. What is the secret in Slim girl? Do people really finds pleasure in such bodies. They are interested in them. In films also there are not any Fat Heroine. They are all slim.? Tell me why do you like slim Girl?