Bile aids in fat digestion and also rids body of some of its cholesterol. Most of cholesterol in blood comes from liver and not food. Therefore, they are not empty calories. Fiber is also carbohydrate. It cannot be digested.
Insoluble fiber adds bulk to stools.
Fiber speeds up transit time through intestine. Fiber also helps prevent colon cancer. Low carbohydrate diets are considered. Fat free foods are loaded with sugar. Leptin, hormone produced by fat cells is released into blood.