In the Mexico case, they aren't comparing actual consumption; they made a model of where they think consumption would have been without the tax. They also show

In the Mexico case, they aren't comparing actual consumption; they made a model of where they think consumption would have been without the tax. They also showed no increase in consumption of untaxed items. If their projections are accurate, that means that all those calories simply vanished from public consumption, not that people shifted to healthier, untaxed foods. So, if these numbers are legitimate, we should see corresponding weight loss among the population.