I am fascinated because I have seen several reports that everything is getting fatter, not just humans; disturbingly, this included lab animals on rigidly controlled diets. I was trying to think of things that might account for that, like antibiotics (which contribute to weight gain) permeating the biosphere. If it's air pollution, well, that's everywhere, albeit in different amounts. It would be interesting to record the levels of pollution and weight in different places and then compare to see how closely air pollution correlates with fat. This finding invites a lot more research to explore how solid it is and how it works.
On the bright side, pollution is one of the more fixable problems we have. There are many ways to fight it, from switching to green energy to filters and scrubbers to planting trees. Individuals can also choose to move from a filthy city to a cleaner countryside.