For years, the party line from the American Heart Association, National Institutes of Health, World Health Organization, and others was to reduce dietary fat. They generally called for limiting fat intake to under 30 percent of daily calories. There wasn’t much evidence to support the notion of low-fat diets in the beginning. (38) There is even less now. Numerous reports over the years have questioned the wisdom of recommending low-fat diets for preventing or retarding heart disease.
http://www.hsph.harvard.edu/nutritionsource/fats-full-story/
I’ve frequently heard that it is better to trim the carbs. An extreme is the Atkins diet.
Reduced fat introduced increased carbohydrates in order to make food appealing. The pasta in “diet” dishes is horrible for me.