Asians have less muscle mass because they don't exercise, not because its a default. There's barely any gym culture in Asia (although currently it's starting to grow) and in terms of beauty, muscle on a woman is considered less attractive because its a masculine trait. If you're a muscled woman, or fat woman, your aunties will for sure nag you to lose weight. Anyway, a round/chubby face on a thin body is a genetic trait. This is why you will see thin or muscly asians who might still have that round/chubby baby face. You typically see this on southern Chinese versus northern Chinese. Southern Chinese (who have more Han characteristics) also tend to have wider noses, double eyelids, a wider face, etc, than Northern Chinese, who look more closer to Japanese/Korean/Mongol people, with longer noses, higher foreheads, monolids,etc.