Fat is not the universal scourge it is made out to be. EVERY diet needs an absolute minimum of certain combinations of fat.
Trans-fats, created by the hydrogenation of unsaturated oils, does not normally exist in nature, and is utilized only poorly by the body. Certain other triglycerides, as found in butter, consist of relatively short-chain esters, including propionic, butyric, capric and capriolic radicals, and are burned readily as energy sources by the body, while the long-chain radicals are burned much more slowly, and have a tendency to remain in storage until forced into the bloodstream by extreme starvation or extreme exercise routines. Literally, you have to be sweating Crisco to get rid of these long-chain radicals. You also risk developing a condition called "ketosis" when your body begins utilizing these long-chain radicals.
The risk of developing "ketosis" is exceedingly small!