Agreed on the diet theory. I find those population studies surprising, given the proportion of medium chain FAs in coconut oil.
Are those populations south Asian? I ran across something in one of Peter Attia's podcast interviews indicating that there's a higher percentage of 'skinny fat' body types (with associated insulin resistance issues) in that population, which may or may not have a bearing here. Wish I remembered exactly which one or with who. Podcasts are not exactly search-friendly. And it was a side comment, unlikely to be in the show notes... It might have been in the one with Mukarjee(?) I'll give that one a re-listen.