Samhita asks why Western beauty norms have changed lately to ever lower BMIs, and also why they are based on whiteness.
One of the most solid things about the transmission of culture is that people imitate those who are above them in the social hierarchy (note: this is vastly oversimplified). You see this with language, when pretentious Anglophones load their speech with French words, and pretentious non-Anglophones load theirs with English words.
This is why in cultures where food is scarce, plumpness is considered ideal. It signals that the woman is prosperous enough to be well fed. It’s also why Indian beauty standards prize fair skin: it traditionally indicated that the person didn’t have to work outside in the Sun.
Now, you might think that modern societies prize thinness for the same reasons less prosperous ones prize plumpness: in the age of junk food, it’s hard for the lower and lower middle classes to maintain a sub-25 BMI. This is especially true in the US, a massive exporter of culture.
This might be a contributing factor, but a) American society is too class-unconscious to have anything as explicit as that, and b) the idea that fatness is bad predates the obesity epidemic. Kids got beaten up in school for being fat in the 1950s and 60s, when a substantial fraction of American households were food insecure.
Instead, what I think contributed to it is the fat cat stereotype. The link between richness and fatness was always there, but cartoons from the robber baron era helped convince people of a link between fatness and piggish, lazy, authoritarian richness.
The best way to check that is to see when fatness began to be seen as bad – for example, when kids started to get bullied in school over this. If I’m right, this will have happened in the very early 1900s, or in the 1930s, two periods when the American poor were very class conscious.
The answer to Samhita’s race question is easier, albeit depressing. Globally, the most dominant ethnic group is Caucasians. The second most dominant and the fastest rising is East Asians. The third most dominant is South Asians. I’m fairly certain that if you look at ethnic breakdowns of lists of models, whites will be the most numerous, followed by East Asians, followed by South Asians.
This is less trivial than it sounds. There are fewer Indians than Latin Americans in the global upper class. It just so happens that most Latina models either are or look like they are of unmixed European ancestry.
So if you’re concerned about the underrepresentation of East Asians or even South Asians in beauty standards, wait 20 or 30 years. Things will look different when China and India start matching the US in their level of exportation of culture. If you’re concerned about the underrepresentation of Africans, though…