Starving women, female athletes and anorexics with low fat stores experience secondary amenorrhea.
It's true that anorexics will literally starve themselves, but this behavior is actually an attempt to use control over food as a coping mechanism for more severe emotional problems.
Generally, people who suffer from bulimia do not lose as much weight as anorexics.
Some experts have observed that many female anorexics were victims of childhood sexual abuse.
It is possible that certain anorexics are using a refusal to eat as a way to avoid coping with the feelings and physical changes that accompany sexual maturity.