Oils and fats are the most concentrated foods we have. Weight for weight, they contain more than twice as much fuel or energy value as any other food. Taken in moderation they are easily digested, but if taken in excess they become a burden to the system. About 7 or 8 per cent of the weight of a normal body is fat, and this fat is formed chiefly from the fatty foods taken into the system, supplemented by the sugar and starch.

When the body becomes very fat, it is a disease, called obesity. Fat people are never healthy. The fat usurps the place that should be occupied by normal tissues and organs. It crowds the heart and the lungs, and even replaces the muscle cells in the heart. The result is that the heart and lungs are overcrowded and overworked and the blood gets insufficient oxygen. Not only the lungs pant for breath after a little exercise, but the entire body. Much fat is as destructive of health as it is of beauty. Those who find themselves growing corpulent should decrease their intake of concentrated foods and increase their physical activity.

Our chief sources of fat supply are cream and butter, vegetable oils, nuts and the flesh of animals. Most meats, especially when mature, contain considerable fat. When the fat is mixed in with the meat, it is more difficult to digest than the lean flesh. Fresh fish, most of which contains very little fat, is digested very easily, while the fattest of all flesh, pork, is tedious of digestion.

There is an instinctive craving for fat with foods that contain little or none of it. That is why we use butter with cereals and lean fish, and oil dressings on vegetables. In moderation this is all right. Fats are not very rich in salts, which must be supplied by other foods.

Because of their great fuel value, more fats are naturally consumed in cold than in hot climates. The Esquimeaux thrive when a large part of their rations is fat. Such a diet would soon nauseate people in milder climes.

Fats and oils are used too much in cooking. Fried foods and those cooked in oil are made indigestible. Sometimes we read directions not to use animal fats, but to use olive oil or cotton seed oil for frying. It is poor cooking, no matter whether the grease is of animal or vegetable origin.

So far as food value and digestibility are concerned, there is no difference between animal and vegetable fats. Fresh butter is very good, and so is olive oil. Some vegetable oils contain indigestible substances. Cotton seed oil and peanut oil are much used. Sometimes they are sold in bottles under fancy lables as olive oil. The olive oils from California are fully as good as those imported from Spain, Italy and France and are more likely to be what is claimed for them than the foreign articles. In the past, much of our cotton seed oil has been bought by firms in southern Europe and sent back to us as fine olive oil! Such imposture is probably more difficult under our present laws than it was in the past.

Most oils become rancid easily and then are unfit for consumption. If taken in excess as food they have a splendid opportunity to spoil in the digestive tract, and then they help to poison the system. Taken in moderate quantities they are digested in the intestines and taken into the blood by way of the lymphatics. They may be stored in the body for a while, but finally they are burned, giving up much heat and energy.

Taking oils between meals as medicine or for fattening purposes is folly. People get all they need to eat in their three daily meals. Lunching is to be condemned.