Now that we’ve seen the good qualities of fat, let’s look at the flip side. Fats are healthy when they come from whole, natural, unprocessed foods. The problem is when fats become damaged. Fats are damaged by heat, light and oxygen. High heat and chemicals used by manufacturers to process oils are the chief sources of damaged fats. One particularly damaging process is partial hydrogenation, which gives oils longer shelf life. This process creates trans fats and other altered molecules that are harmful to the human body.