I was not ignoring your argument but rather pointing out that there is data showing a correlation between doctors advocating low fat/high carb and obesity in America.
Now, what is a straw-man is to put forth a theoretical/never seen in reality diet and claim that no one has ever gotten fat eating it. Sorry, but an extrapolation from a population of zero to 350 million is a bit much for me.
I think the one point we do agree on is that this is a complex issue. So, you can blame fat people for not listening to their doctors, doctors for not checking the research or food companies for bastardizing what doctors actually recommended to sell low fat/high sugar food and label it "healthy." But it's quite obvious that the advice doctors have been giving for the past few decades has not had the intended effect.