Another problem with low fat is that there's lots of evidence that it's effective--with the disadvantages given--when people or animals follow it/are forced to follow it. Mice in cages, humans in metabolic wards or in places where there wasn't enough available dietary fat to make a major part of the diet on average for the population. But telling people not to eat fat hasn't been very successful. People either don't do it, or compensate by eating more sugary foods, or foods designed one way or another to be hard to stop eating. Or they'll eat low fat pizza, low fat ice cream etc. all week, and then binge on the real thing on the weekend. There's a study showing if you feed rats fake fat potato chips sometimes, full fat type the other, they get fatter than if fed just one, or just the other--maybe the two similar foods don't predict calories from fat very well, so the animals sort of ignore the fat.

If people are to be free, and they should be, what they can be convinced to do of their own free will is as important as relative effectiveness.