It is possible for one to live and grow when eating only vegetable matter. But the boy or girl who tries to become a strong man or woman by eating only vegetables will be disappointed; these are mostly heat-producing foods and will not make strong bodies. Experience has proved that the best results are obtained by eating what is called "a mixed diet," that is, a diet composed partly of lean meats and partly of fats and vegetables. [Sidenote: The heat-producing foods] Of the heat-producing foods, fat is the most powerful. Most of the fat that we eat is used immediately for producing in the body heat, and therefore power, but a part of it is stored up for future use. We see it in all healthy young persons. It is this stored-up fat that gives the body its rounded form. When any one has been sick he is thin, because, to produce heat and power while he was sick, he has had to use the fat stored up in his body. To have such a supply of fat is like having a bank account to draw on when out of work. We might call the deposits of fat in our bodies our health banks. Fat meat is not the only form in which we eat fats; we eat them in a great many other ways. Certain vegetables, such as beans, contain an oil that forms fat. Ripe olives contain a great deal of fatty oil. Butter is a very important form of fat, and cream contains a large amount of it. [Sidenote: Cost of suitable foods] In selecting our foods we should think of two things: _first_, the value of the food as a heat-producer or as a building material; and _second_, the cost of the food. We may like butter much better than bacon, but we should remember that, pound for pound, bacon has a greater nourishing power than butter, and a pound of bacon will cost far less than a pound of butter.[1] Vegetable foods produce heat by means of the starch which they contain. All vegetables contain starch. This starch is changed into a kind of sugar in the body, and when thus changed it is used to produce heat and power. All vegetable foods do not have the same heat-producing power. There is more heat-producing power in a pound of oatmeal than there is in ten pounds of cabbage. Ten cents' worth of dried beans will produce more heat in the body than will a dollar's worth of lettuce. Thirty cents' worth of corn meal will do more building in the body than will a piece of mutton worth a dollar and a half; but you would have to eat a large amount of corn meal in order to secure the building effect that would result from eating a small quantity of mutton. In most fruits the only nourishing quality is in the sugar they contain. This sugar produces heat in the body just as starch does. [Sidenote: The real value of advertised foods]