Carbohydrates and fats are interchangeable as fuel foods, but it can be shown, by calorimeter, that fats produce more than twice the heat energy produced by carbohydrates. One gram of fats yields 9 cal, while 1 gram of carbohydrate yields 4 cal. An additional advantage of fat form viewpoint of energy availability is that it stores well in large amounts in adipose tissues. Thus fat, considered to be a reserve form of fuel for the body, is an important source of calories.
Paradoxically, this is not advantageous in affluent societies where the problem is not the availability of food for energy, but rather the health hazard of obesity. Fats may occur in foods as materials that are solid at room temperatures or as oils that are liquid at room temperatures. Solid fats contain comparatively small amounts of fatty acids with two or more groups of adjacent carbons that are not fully saturated with hydrogen.
Healthy diet component: Fats