What is a Normal Diet

By Frank W. Britton, D.Sc.
London, England
The calculation of a diet from definite scientific data is comparatively easy provided certain tables are first compiled giving the amounts of the three essential groups –proteins, carbohydrates and fats per ounce or pound of foodstuffs selected.
Diet Controls Disease
Indeed, diet constitutes one of the fundamental factors by which disease may be controlled, and research has proved that there is a definite relationship between the heat values of different foods and the bulk of the body. This caloric value depends upon the nature of the food, i.e., whether it is rich in protein, carbohydrate or fat, and the balance between these three must be established. Also, this relation must be in such a ratio that the amount of fat should equal twice the amount of carbohydrate plus half the amount of protein –such amounts being in grams.
In this respect the caloric value of one gram of fat is 9.3 calories, of carbohydrate 4.1 calories, and that of protein 4.1 calories –the calorie used in physiological work being the “large calorie” –viz., the heat necessary to raise one kilo, of water one degree.
A factor which must also be considered in such calculations is that of muscular exercise, for any great departures from the normal are likely to involve greater loss of heat and excretia from the surface of the body, due to an increased metabolism, so that this loss must be compensated for by a slight “over-fuelling” of the body in the form of increased amounts of proteins, carbohydrates and fats.
However, it is advisable to base our calculations upon the “average normal or basal metabolism of the body” engaged in moderate exercise and to allow slight variations, plus or minus, according as our physical activity approaches the resting or “working” phase.
I have based the following calculations upon the formula given above regarding the amount of protein, carbohydrate and fat in grams, and reference to the tables will show the proportion of these in a given weight of foodstuff.
It is quite easy to work out the exact requirement in the following manner, allowing ½ gram of protein per pound of body weight. The weight of the body in pounds must first of all be multiplied by 20; this gives the approximate daily calorie requirement, which must be divided to give the correct proportion of protein, carbohydrate and fat.
Since we allow ½ gram of protein per pound of body weight and, multiplying this quantity by the calorie value of protein –viz., 4.1 –this, subtracted from the total caloric requirement of the body (weight in pounds x 20) will leave a certain number of calories to be divided between the carbohydrate and fat.
After allowing ½ gram of protein per pound of body weight, this multiplied by 4.1 is subtracted from the product of the body weight and 20, leaving a certain number of calories for division between carbohydrate and fat.
This number must be divided by the arbitrary figure 26, thus giving the amount in grams of carbohydrate required.
After multiplying it by 4.1 (the caloric value of carbohydrate), it is added to the protein calories and deducted from the total number of body calories, the difference representing the number of fat calories.
Knowing the number of fat calories required per day, its weight is found by dividing them by 9.3 (the caloric value of fat). Hence the amounts of protein, carbohydrate an fat may be readily adduced in terms of daily rations.
An Example
We will take an example of a man weighing ten stones engaged in moderate exercise. Obviously he requires 140×20 or 2,800 calories per day, which must be divided between protein, carbohydrate and fat in the correct proportion as shown in the above formula.
Allowing ½ gram of protein weight, this equals 70 grams or (70×4.1)=287 calories of protein which deducted from 2,800 leaves 2,513 for dividing between carbohydrate and fat. If this number is now divided by the arbitrary figure 26 we are left with 96 grams or (96×4.1)=393 calories of carbohydrate.
Adding these to the protein calories and deduction from the total gives us: 2,800-(287+393)=2,120 calories or (2,120/9.3)=228 grams of fat.
Thus, a man of 140 lbs. weight engaged in moderate exercise requires 70 grams of protein, 96 grams of carbohydrate and 228 grams of fat per day, which agrees with the formula given: 2C+ ½ P=F, or