> That's great news though I'm a little suspicious, where have taxes caused a significant change in body weight?

You could check https://en.m.wikipedia.org/wiki/Sugary_drink_tax as a starting point. From a skim it doesn't look to me like a small tax is some kind of miracle cure for anything in this regard. Though I don't think anyone claimed that it would be the one factor that fixes everything. There is no one factor, and having the tax as part of a toolbox seems reasonable.