None of these warning signs on its own means that a young person has anorexia but if they are exhibiting several of these signs then you are right to be concerned.
Other posts you may find useful
10 warning signs that a young person might have anorexia
5 useful phrases when talking to someone with an eating disorder
Healthy weight loss can put young people at risk of anorexia
Teaching pupils about eating disorders
Weight change – the ultimate eating disorder warning sign