Almost all of us have been taught to hate fat. Unless we have spent considerable effort understanding and challenging our cultural obsession with thinness, we automatically condemn fat in ourselves and others. Think of the last time you shopped for clothes. Young people are not stupid. They perceive our beliefs and biases even if we try to hide them.
Children learn such attitudes quickly.
In one study of girls ages nine to eighteen, every one feared being fat. They all believed that dieting is the normal way to eat. It isn't, of course, but lots of people think it is. Young people are so preoccupied with thinness that in many cases they lose the ability to see themselves realistically. Consequently they wanted to lose weight.