I agree this would be a very important Problem to solve. However I think that the root cause of this problem is that the food industry has the incentive to maximize profit. Since sugar ist cheap and tasty for a lot of people the obvious thing to do is to sell as much sugar as possible. Of course sugar is just an example here, the same logic could be applied to other products (cheap fat, fast food).
IMO the general aproach to maximize money is broken as it incentiveses crminal behavior (banks, volkswagen come to mind immediately). This problem would be really interesting to solve, but I don't think that's doable by a single startup as it is a political or social problem.
It would be interesting to see absolute numbers. I remember vaguely that the productivty increased by a factor 8 since the eighties...