What are warning signs of male anorexia?

The same. The signs of anorexia are the same for men and women. Essentially, it is denying oneself of nutrition, losing weight so that you are well below a healthy weight for your height, both coupled with the belief that you are not thin enough. Anorexia can be a very serious condition. Other things can cause a poor appetite and weight loss, such as depression or a medical problem. Hope this helps.