I'm afraid that more recent thinking had decided that simple carbs are easily broken down and are stored by the body as fat and more complex carbs are also easily broken down and are also stored by the body as fat.

Carbs are digested and moved into the bloodstream as sugars, where they can damage the retina and blood vessels, kidneys, etc., so there is an immediate release of insulin which removes the sugar and stores it as fat. Usually the rapid drop in bloodsugar results in a sensation of hunger and so you eat a sandwich or sugary item or have a sugary drink and the same sequence is repeated.

Fats, on the other hand, first of all are not all absorbed, and secondly, when they are they are left in the bloodstream so as to be available to provide energy. There is no insulin spike blood sugar crash sequence.