What they have done is an initial analysis of several candidates for a chemical cause for the obesity epidemic to try to figure out which might be worth doing f

What they have done is an initial analysis of several candidates for a chemical cause for the obesity epidemic to try to figure out which might be worth doing further tests on. They use whatever publicly available data they can find along with some logic and some reasonable guesses. For a summary of their conclusions about what further tests would be interesting go to the last page. It does seem likely there is something in the water, but some further experiments would be needed to prove that. Overall the set of articles is a great example of how to find a scientific hypothesis to test.