Never trust a father who insults your weight and tells you that "You wouldn't look that way if you tried harder." When I've been trying everything to get skinny
I was going to comment about where the need for you to be skinny is coming from, but I’m going to assume its a health issue/none of my business and focus on the first part of your message.
I agree, never trust someone, who is supposed to care for you and love you, when they criticize you over trivial things like the way you look and how skinny or fat you are. Why does that matter to him? Why does he care? Making value judgments about you based on weight is ridiculous and cruel.