This study is not an isolated case regarding the issue of bacterium-mediated weight gain.
There have been several studies which clearly indicate that there appears to be a case for "(at least some) people have excess weight due to 'which bacteria inhabit their gut' " or something approximating that.
Yes folks, I said DUE TO, ie caused by the bacteria not the other way around (in at least one case, administering a certain bacteria caused not just scientifically significant but visibly large weight gain on the exact same diet, at least in rats).
As yet there's no conclusive proof (ie several repeated tests independently verified) with hard science numbers (not to mention something of an explanation why/how this works) and, and no magic cure for fatness, but science is nowhere near laughing this off as 'mere crackpottery'.
There's VERY OBVIOUSLY something going on here with certain bacteria and (at least) some overweight people, and scientists (all over the world, not "just someone I've never heard of in China") are turning up results from a variety of research projects (all with slightly different angles) all pointing in the direction of "this is starting to smell just like That Stomach Ulcer Thing".