From DietDoctor.com — a look at the change of macronutrient composition in our diet from 1971 to 2000. As we transitioned to the recommended low fat approach our carbohydrate intake increased dramatically. It had to, because there are only three macronutrients: carbs, protein, and fat. If you restrict fat you will by default consume more carbohydrate-rich foods.
The LCHF approach flips this to reduce carbs (sugars, starches, grains) and increase the fat content. The typical result of this is healthy weight loss as well as improvements in several metabolic markers like HDL, triglycerides, blood pressure, and insulin sensitivity.
Another look at macronutrients and associated effects from this study.