Okay, while we're comparing alcohol and sugar.
Currently, the government caps alcohol manufacturers on the ABV of their beers. Major manufacturers respect these policies without much issue and the only people that would probably go around them would be microbrewers (which really isn't a huge issue in the scheme of things).
Similarly, what if the government instituted caps on the amount of sugar that could be added to certain food products? I think it could work pretty similarly to the current ABV caps. The sugar refiners would pitch a fit, sure, but it wouldn't cost the manufacturers anything extra and I don't think the prices would be affected. If the manufacturers went over their caps, they would be fined an appropriate amount, which would discourage the practice. Since these policies would be applied universally, no company would gain an edge over another due to the change in recipe.
I think that a huge part of the obesity issue starts at the manufacturing end of foods and stems from the practice of adding lots of sweeteners to foods. As well as the immediate fat deposits gained from the excess sugar intake, our taste buds are trained to expect sweetness. It'd be difficult for any one manufacturer to lower their sugar content and expect to remain competitive due to the public's expectations of sweetness. Government policy is really the only way I see of exiting this conundrum.
Or maybe it would be 1984 combined with Logan's Run. I don't know.