Animal fats like butter or lard are hard at room temperature because there are few or no missing hydrogen atoms. For more on this process, click here. Our bodies do not readily recognize these artificially saturated fat molecules. Thus, they are difficult to digest, and stay in the body a long time. This can cause weight gain and digestive troubles.
Hydrogenated fats are high in trans-fatty acids .
Researchers at the Harvard School of Public Health and the Wageningen Centre for Food Sciences in the Netherlands took a look at 25 studies on the subject and concluded, in the prestigious New England Journal of Medicine, that the more trans fatty acids you eat, the higher your risk of a coronary disease. When fats break down in the body, one of the products are chemicals called prosteglandins, which regulate certain body processes. Prostaglandins help control inflammation, and are used by the body in many ways, for instance during sex, or after you twist your ankle. Some prostaglandins cause inflammation, others work against it. Hydrogenated fats break down into prosteglandins which cause inflammation, throwing off that delicate balance and leading to chronic inflammatory diseases and pain.