The cereal you said is not high in calories. A bowl of cereal 135g has less calories than 100. Moreover, the fiber in the grain is soluble fiber, which is of great benefit to the body. Eating low-fat milk and boiling cereal has a good effect on losing weight. Everything is added in the supermarket, such as sugar, milk powder ... The calories are very high.
Water has no heat. If it is oatmeal soup, the calories are lower. It is true that the heat has nothing to do with the amount of water put in. As long as it is not sweet, the heat is not high.