I traveled to India a month ago for business, for the first time in 20 years. I noticed some changes - more scooters, more cars, fewer pedestrians, actual luxury cars and big motorcycles. But the in-your-face difference was obesity. In 2004, there was virtually none; everyone was what we Americans would call skinny. I mean, at 6'2" I felt like a giant, but at 6'2" #180 I felt like a porker. Now... now the locals look a lot more like us. Less walking, more A/C, worse pollution. Subway, McDonalds, TGI Fridays. My local friends from 2004 tell me "kids these days" aren't staying vegetarian, eat out more, drink alcohol.
I'm sure there's some natural variation, but I'm not convinced that being naturally thin is an overriding thing. An entire country didn't lose their natural thinness in a generation.
On the other extreme, Audax has exploded in Asia generally, and in India in particular.
I expect the common denominator in the above extremes is disposable income and the related free time. So I'm frickin' doomed.