I recently ran across this article published in Current Obesity Reports calling for more rigorous methods to assess the effects of soda and fat taxes. The article makes a number of good points, but it also misses many more complications that should be included for a rigorous evaluation - for example, how do firms respond when subjected to new food policies?
Another example comes to us via this paper in the Journal of Marketing by Debabrata Talukdar and Charles Lindsey. If you want to tax unhealthy foods and subsidize healthy ones, the authors suggest regulators may face an up hill battle because consumers are less sensitive to rising prices for unhealthy foods and falling prices for healthy foods than the reverse.
A portion of the abstract: