Fats are used to absorb or get nutrients, like Fat-soluble Vitamins for humans. It is used as a source of backup energy in cases when carbohydrates are not available, or people can not use it at that time. People need more than 20 to 35% of daily calories from fat. Also, fats play a role in helping people's body maintain or keep the core (center) temperature. However, they are also harmful, in other words, they have bad effects on human's bodies.