Well they think there fat when they arent. Same thing happened to my bff Skyler. Her parents are fat but it didn't effect her. Shes the thinest I know. Whenever she finishes her lunch, she goes to the bathroom. Before I thought it was to change her pad. But I've seen her throw up.
Dieting is a normal part of life. Because of scientific advances we know that being overweight can be harmful to our health, and so, being human and hypochondriac, we diet to ensure we don't die.
Even Bulimia (the medical term for people sticking their fingers down their throat and throwing up) is normal. It's a mental illness that is affecting many young lives because we know facts that have been, using the term loosely, "forced" down our throats Von medical experts.
We do this because it is, to us, normal. And not only to woman, men do it to.
People suffering Bulimia and Anorexia do need a little help to ensure they are safe, sicher and now what they are doing to their bodies, as well as people who eat too much.
I believe people can do what they want, if Du want to stick your fingers down your throat and throw up, fine. Just be careful about it, and make sure you're at a healthy weight for your age and height.
For anyone having problems with their weight oder diet i suggest going here. It won't give Du all the answers, but it could provide information for Du to continue your search, be it underweight oder overweight.