While "Good Calories, Bad Calories" (great book, hate the title) is generally known for being a "low-carb book", actually the bulk of the book is an in-depth examination of exactly how we got to the point where "low-fat diet = good" is not just a dominant hypothesis but borderline religion. If you are truly interested in an answer to that question, this is it in book form.
The short answer is, indeed, politics, but I actually blame scientific politics rather than traditional government politics. The latter enabled the former to really spread its influence, but had the strongest personalities in the dietary movement agreed that fat is harmless, the government would never have ended up rubber-stamping the low-fat dietary dogma. The longer answer is, as sliverstorm said, the look-under-the-lamppost problem; we got a couple of cheap measurement tools early and then extrapolated the hell out of the small, small, oh-so-small view of the complex system we had.
Incidentally, we do that all the time and continue to do that. Almost every article I see online about how X is bad for you or how Y is good for kids can be traced back to a study that boils down to a point sample in the n-dimensional space of like; such things are often only marginally better than nothing, all of our best scientific controls notwithstanding. The next great revolution in science as a whole is going to have to be figuring out some way to get a holistic view of more things, we're drowning in data points that often add up to nothing.
The short answer is, indeed, politics, but I actually blame scientific politics rather than traditional government politics. The latter enabled the former to really spread its influence, but had the strongest personalities in the dietary movement agreed that fat is harmless, the government would never have ended up rubber-stamping the low-fat dietary dogma. The longer answer is, as sliverstorm said, the look-under-the-lamppost problem; we got a couple of cheap measurement tools early and then extrapolated the hell out of the small, small, oh-so-small view of the complex system we had.
Incidentally, we do that all the time and continue to do that. Almost every article I see online about how X is bad for you or how Y is good for kids can be traced back to a study that boils down to a point sample in the n-dimensional space of like; such things are often only marginally better than nothing, all of our best scientific controls notwithstanding. The next great revolution in science as a whole is going to have to be figuring out some way to get a holistic view of more things, we're drowning in data points that often add up to nothing.