Currently, a BMI of 24 is considered “normal” weight in America– even though one’s optimal BMI is below 22 (assuming that you have an unusual body composition or are some sort of athelete) and starts to take a downturn for diseases such as diabetes around a BMI of 22. By contrast, a BMI of 17.5 (102 lbs on a 5′4″ frame) is used as one diagnostic criteria for anorexia in the West. Being a skinny girl doesn’t constitute “anorexia”–and cut-offs used should accurately screen people with weight distortion issues from some skinny girl. A significant proportion of SE Asian women would be classified as “anorexic” based on Western-imposed standards.

BMI of around 18 is quite common in Asia and is does not mean that it is an “unhealthy” weight—As a researcher, I would much, MUCH rather have a BMI of 18 (technically classified as underweight) than 24 (currently classified as normal) from a health standpoint for most chronic diseases (with the exception of osteoporosis).

In Japan, Hong Kong and Singapore– large percentages of the population are “underweight” but note that these countries also have the longest life expectancies in the world. Most lay people in these countries would consider a BMI of 18.5 as “slim” for a woman (108 lbs on a 5′4″ frame) and 17.5 as somewhat underweight (102 lbs or less) and anything over a BMI of 21.5 would be considered “fat” (125 lbs) and BMI>27.5 would be seen as extremely fat (160 lbs)– (comparable to what Americans would perceive a 220 lbs woman to be).

One argument that is generally put forth about Asians versus Westerners is that Asian a smaller boned. This argument doesn’t really hold much water.

One bone mass does not account for the enormous BMI differences between Asians and Westerners– bones account for less than 15% of your body weight, and fat people’s bones will always be grow heavier to support the extra load and shrink when they lose weight. Even so, a ‘large-boned’ woman versus a ’small-boned’ woman, if you were scrape off all their meat and weigh their respectives skeletons, the difference would be less than 10 lbs on a standard 5′4″ woman– assuming that the small-boned woman doesn’t have advanced osteoporosis. Take a look at old photos of Auschwitz survivors, famine victims– there is little visual difference in bone mass between people of similar height. One’s bones shrink with starvation as does one’s musculature.

I believe that the WHO and the American Dietetic Association should revise their BMI standards to get away from the Western cultural biases. But they won’t because millions of Americans will scream bloody murder. ADA doesn’t want millions of people blaming their self-esteem issues on them. Moreover, they won’t want to have to live up the stringent standards that they set up for themselves.

If you don’t believe me, try attending a conference of the American Public Health Association– you will note that quite a large percentages of the members have BMI>30 and a noticeable % are morbidly obese (I mean nearly as wide as they are tall). Most of the non-obese people are foreigners.

Anyway, regarding the graph. The problem with it is that it doesn’t discriminate well between people who are at a BMI, say 18-ish which isn’t much of a health problem versus the % who have a BMI of <15– which is a big health problem (organ failure, infections etc). I suspect that the majority of those Japanese people shown have a BMI from 17-18. From a clinical standpoint, they can stand to gain some weight but are not in danger or having scurvy or beri beri or dying of starvation.