It's not hard to see Americans are getting fatter by the minute and I think our diet is to blame. People eat crap and too much of it. Rather than tax sugar, I would set up a sliding tax based on the number of ingredients. If you buy something like an apple or an onion, you pay no tax. If you buy something with 2-5 ingredients, you pay maybe a 20% tax. Something with 6-10 ingredients would have a 50% tax and so on. I would eliminate all other taxes on food. Yeah, it would make some food become prohibitively expensive, but that would be the point. And no, bread wouldn't count as one ingredient. In fact, modern bread would be heavily taxed because it is enriched beyond belief.
Perhaps my tax is too harsh, but the idea would be to discourage people from buying anything, but whole foods.