This is a mischaracterization of the past 30 years. In the 1980s, American's really were told to drastically reduce their fat intake due to a misunderstanding of LDL. It remains recommended to only be 10% of your daily intake of calories -- a statement of the percentage of calories you should eat as fat, not a statement about excess calories, which can be regarded as bad in general regardless of their source. If you look at what took place in the following 30 years since this stance, fat intake has in fact been reduced quite considerably in the United States, yet heart disease has increased. This has nothing to do with worshiping "ancient wisdom", its simply identifying an error science made (which it is allowed to do), and rectifying it without historical revisionism.