Why should you limit your intake of oils and sugars?

The recommendation to reduce saturated fat consumption is based on the assumption that high serum cholesterol "causes" arteries to clog. At the time scientists formulated this hypothesis it was not known that inflammation in the arteries is what causes cholesterol to be deposited. Absent inflammation, high serum cholesterol is harmless.

Since certain chain lengths of saturated fat elevate cholesterol, it was assumed that restricting saturated fats would furnish protection from Heart disease. Unfortunately, all the studies that linked saturated fat to increased mortality from heart attack failed to distinguish the effects of omega-6 trans fats from saturated fats. Consequently, saturated fats became the whipping boy for omega-6 fats. Excessive omega-6 consumption is now believed to be responsible for the inflammation that leads to clogged arteries.