Why has Fast Food Nation failed to produce any level of reform to the fast food industry?The Jungle profoundly affected Theodore Roosevelt and...

It's a wonderfully fascinating theme you are suggesting.  The answer will be more lengthy and indepth than what I can offer here, but I hope to develop a start.  One primary reason why reform in the fast food industry is not as apparent as Sinclair's treatment is the time period.  At the time of Sinclair and Muckrakers, there was a distinct feeling of progressivism and an embracing of structural change.  Questions about capitalism and the free market started to emerge because its wide level of success had been relatively new.   Progressivism happens within the same time frame as the titans of industry emerge.  This means that the social "cement" was relatively new, and able to endure some level of change and malleability, into which Progressivism fit in quite nicely.  Contrast this with Schlosser's study and one sees that capitalism and market economics is firmly embedded into the psyche of America and American consumerism.  This translates into a greater level of inertia to change.  McDonaldization is not only an idea, but, in a manner of speaking, a way of life that is firmly embedded in America, and thanks to the power of globalization, the world.  Massive reform, like the kind called out after reading Schlosser's work, is not going to be easy in such a setting of economic resistance.

One of the critical elements of Schlosser's work calls for a fundamental reexamination of American dependence on fast food.  After reading the book, one gets the impression that this reexamination has to be one of abandonment for there is little good for us and our nation in such a condition, being at the whim of the fast food conglomerates.  A reason why this has not been embraced by the consumer might be attributable to the recent economic downturn.  Frankly speaking, economic difficulties have impacted many an American.  Some might be working extra time or overtime, or even an additional job or two in order to meet the demands of the current state.  Others might be out of work, or in transitional phases.  This puts health concerns into a different context, and economy in terms of simplicity, direction, and "cheap eats" take primacy.  When so many fast food establishments offer "value meals" or "Five Dollar Boxes," people seem to prefer this out of convenience and economic conditions. This is especially valid in the urban centers, deemed as "food deserts" for the lack of healthy alternatives. Seeking a different approach to nutrition, which might involve either a time commitment or greater economic cost when that is not present, might be a reason why change has not been so rampant.

I would suggest that there has been some level of change  in the approaches of fast food restaurants, and while not to the level of implication in Schlosser's work, there have been some changes.  Restaurants are being told to offer more "healthy" alternatives to their menus.  Smaller portions are being offered, and recent legislation has been passed that demands caloric and nutritional information be prominently displayed.  In an industry that has become such an embedded part of our capitalist and free market social and economic orders, this change is significant, and only brought about by the voices of Schlosser's work and others.