Male anorexia is fairly common, it’s just hardly ever portrayed in media because it’s not “masculine”. It happens, and often sufferers won’t realize they’re sufferers because they don’t recognize their symptoms as an eating disorder. And to answer your questions, eating disorders affect a broad demographic, with no concern about sexuality, age, race, or gender. Eating disorders are not always white teenage rich girls, that’s just frequently what is seen in movies and shows and books. I’ve seen older men with eating disorders, I’ve seen black women and teenage boys who started doing it because of sports or because they didn’t even realize their “diet” was becoming anorexia nervosa.
Anorexia does not discriminate, and anorexia is way more common than what people would think, it’s just hidden from the public eye.