I'll never know either, but once in London I got to talking to a tiny Japanese woman. The only place she could find adult clothes to fit was at a branch of a Japanese department store there. She hated having to try on children's clothes in a search for fit.
hmmmmm....If it was a friend I would invite them for yummy meals they couldn't refuse! Of course, I would say nothing about their size, just shower them with love, acceptance, and beautiful tasty food.