What Mort is missing is two points. One, a person can become fat without consuming large amounts of fat and sugar. Daily calorie intake and output is what determines body weight in most cases except for those with metabolic problems. Two, it is recommended that a healthy diet contain 30% fat. You body needs a certain degree of lipids to stay healthy. That fat should be more of the monounsaturated variety but saturated fat is not automatically unhealthy if it is kept in a reasonable range. By taxing "unhealthy" fat everyone would have to pay taxes based on saturated fat content. This is would be for everyone not just fat people. Another draw back is that people will tend to turn to low fat processed foods that are loaded with sugar and can be less healthy than having eaten the full fat original version.