Not to mention the fact that when "Almost all experts agree" on a wide range of things, they are almost certainly going to be wrong about at least a few of them. The notions of experts about what sorts of foods make people fat have changed drastically in my several decades of adulthood. They're bound to change again. Will the taxes go away on foods that the latest scientific version of the truth decides are no longer fattening? Of course not. They'll stay, and also be added to the new alleged culprits, as more and more foods fall under the tax.
And then, aside from the food question, there's the question of whether it's in the best interest of government to discourage mental activity and learning (in the form of games) on the dubious assumption that the alternative that people will choose will be healthier.