Let's not forget that "anorexic" does NOT mean "underweight". Anorexia is a mental illness (the most deadly among mental illnesses). Being underweight is another thing entirely. For example, female athletes can easily be underweight: because they have to run and jump, their body fat percentage has to be less than 20-24% which is optimal for fertility. As a result, their bodies may cut on the expense of precious resources and stop menstruating. That makes them clinically underweight, but not unhealthy, and certainly not anorexic. And, as you said, the normal Eastern Asian weight is completely different. I bet the Japanese and Chinese are healthy at that weight.