THE STATISTICIAN looks on nutrition as a matter of calories, and on obesity as a question of upset caloric equilibrium. A calorie is a unit of heat, a unit of potential energy, but not a unit of nutrition. Prison governors, school superintendents, dictators whether of a nation or of a small community, talk in calories to prove that they are feeding their charges or their victims adequately. Fellows of the Royal Society, and doctors with political leanings, talk in calories as if the human body were a machine requiring a certain amount of fuel to enable it to do a certain amount of work.
A motor-car needs calories, and we give it calories in the form of petrol. If we give it good petrol it will do good work for quite a long time. But even a Rolls-Royce cannot find its own fuel. It cannot separate motor spirit and lubricating oil from the crude mixture brought by a tanker from the wells of Kuwait. It cannot clean its own pipes, clear its own choked jets, grind its own valves, re-line its own bearings when they are worn, and replace defective parts as they need renewal. The body can do all these things. but the body is not a machine, and to do them it needs food not fuel.
There are three kinds of food: fats, proteins and carbohydrates. All of these provide calories; the fats 9.3 calories per gramme, the proteins and the carbohydrates 4.1 each. But the carbohydrates provide calories and nothing else.
They have none of the essential elements to build up or to repair the tissues of the body. A man given carbohydrates alone, however liberally, would starve to death on calories, While he was dying he would break down his own proteins to provide materials for the repair of his key organs. He would use what calories were needed to provide energy, and he would lay down the carbohydrate surplus to his caloric requirements as fat.
Proteins are the essential food of the body. They provide not merely carbon, nitrogen, sulphur, phosphorus, sodium, potassium, calcium and iron, chlorine and iodine, but those trace elements such as boron, manganese, zinc, copper, and cobalt that are essential to life. They provide many prefabricated molecules that the body is unable to build up from simple elements.
Fat is the caloric reserve material of nature. The whale stores fat in his subcutaneous layers against the rigours of life at the Pole, the camel stores it in his hump against hard times in the desert, the African sheep stores it in his tail and his buttocks against the day when even the parched grass shall have withered away. But fats are more than stores of reserve caloric material. They are heat insulators, they are fillers of dead spaces, and they are facilitators of movement in rigid compartments such as the orbit, the pelvis, and the capsules of joints. They are also essential building materials. Animal fats contain three groups of substances: the neutral fats which are chiefly energy providers, the lipids containing phosphorus that enter into most tissues and bulk largely in the brain and the central nervous system, and the sterols that are the basis of most hormones.
The body must have proteins and animal fats. It has no need for carbohydrates, and, given the two essential foodstuffs, it can get all the calories it needs from them.
The expert on nutrition is not the nutrition expert, but the man who has studied nutrition by the ultimate method of research, the struggle for survival. The Eskimo, living on the ice floes of the North Pole, the Red Indian travelling hard and far over wild lands in hunting or war, the trapper in the Canadian forests, the game hunters in Africa-these men must find food that gives the greatest nutritive value in the smallest bulk. If they cannot find such a diet, their journeys will be limited both in time and in distance, and they will fail in their task All these men have found that a diet of meat and animal fat alone, with no carbohydrates, with no fruit or vegetables, with no vitamins other than those they get in meat, not merely provides them with all the energy they need, but keeps them in perfect health for months at a time. Seal meat and blubber for the Eskimo, pemmican for the Indian and the trapper, biltong for the hunter, have proved to be the perfect diet both in quality and in bulk.
Dr. Mackarness's book is timely. It brings the important research work of Kekwick and Pawan into the sphere of everyday medicine, and it shines the torch of common sense into a corner that was becoming obscured with the dust of statistics and the cobwebs of scientific dogma. It bears a message of hope and good cheer to the plump.