FACTORS DETERMINING THE FOOD REQUIREMENTS OF THE BODY
For the Adult.—Muscular activity, Age and Size, are most important factors influencing the food requirements. The physical condition and environment of the individual also exert a certain amount of influence upon the intake of food.
Work.—Muscular activity, as already stated, increases the body expenditures; consequently the more active the work the greater amount of energy food needed per unit of weight.
Age.—As the individual grows older, the rate of metabolism decreases until, in old age, it is not more than a third to a fifth of what it was in earlier life. This is due to a general “slowing down” of the machinery, the heart does not beat so rapidly, nor is the respiration so quick. The digestive organs, the heart, the liver, and the kidneys, cannot handle the volume of food which was required during the period of greatest physical activity. Hence, any great excess over and above that which is needed for the maintenance of the body in health will be a source of danger to the elderly person. Von Noorden claims the food requirements of individuals from
60 to 70 years of age to be reduced 10%; for people from
70 to 80 years of age to be reduced 20%; for people from
80 to 90 years of age to be reduced 30%.
Sex.—Science has proved, that there is little difference in the food requirements of men and women, provided they are alike in age, weight and size, and are doing the same amount and type of work. But women, as a rule, weigh less than men, hence their food requirements are approximately less.
Murlin finds the food requirements of pregnant women to be some what higher than of non-pregnant ones, and the requirements of the nursing mother to be higher than either (see chapter on [Pregnancy and Lactation]).
For the Child.—The factors influencing the food requirements are different, to a certain extent, from those of the adult. The main difference lies in the fact that the adult needs food only for the maintenance and repair of the body, while the child must have food, not only to cover its maintenance requirements, but to support the growth and development which should be continuous from birth to maturity. Resistance, too, must be developed during this period in order to safeguard the child through life.
The rate of metabolism in the infant is greater than at any other period of life, consequently, even if a child were one-third the weight of its parent, it would inevitably cease to grow and would become malnourished, if its food requirements were reckoned at only one-third that of the parent.
Adjusting the Food Requirements.—Taking these factors as guides for estimating the food requirements of man, it is evident that no hard and fast law can be laid down to cover all, that each individual must adjust the food intake according to the weight and activity of the body. Sherman has arranged the following table showing the energy expenditures per hour for the average man (154 pounds), per pound of body weight (these are approximate averages only).
TABLE[21]
| Sleeping quietly | 60-70 calories per hour |
| Awake, lying still | 70-85 calories per hour |
| Sitting at rest | 100 calories per hour |
| Standing at rest | 115 calories per hour |
| Tailoring | 135 calories per hour |
| Typewriting rapidly | 140 calories per hour |
| “Light exercise” (stationary bicycle) | 170 calories per hour |
| Shoemaking | 180 calories per hour |
| Walking slowly (about 2¼ miles an hour) | 200 calories per hour |
| Carpentry or metal work | 240 calories per hour |
| “Active exercise” (stationary bicycle) | 290 calories per hour |
| Walking briskly (about 3¾ miles an hour) | 300 calories per hour |
| Stone working | 400 calories per hour |
| Severe exercise, such as sawing wood | 450 calories per hour |
| Running (about 5½ miles an hour) | 500 calories per hour |
| Very severe exercise (stationary bicycle) | 600 calories per hour |
The above table, calculated for an average man weighing 154 pounds, may seem less simple to use than one based on the energy requirements per pound of body weight per hour, of an average individual. For example, a man weighing 123 pounds and performing practically the same amount and type of work as done by the man weighing 154 pounds would require practically one-fifth less calories than the latter individual. Hence, to facilitate the estimation of the food requirements for average individuals, the following table is included.[22]
| Sleeping | 0.42 calorie per hour, per lb. of body wt. |
| Sitting at rest | 0.65 calorie per hour, per lb. of body wt. |
| Light muscular exercise | 1.10 calories per hour, per lb. of body wt. |
| Active muscular exercise | 1.90 calories per hour, per lb. of body wt. |
| Severe muscular exercise | 3.00 calories per hour, per lb. of body wt. |
Possibly a few explanatory words, as to the terms used in the above tables, will assist the nurse in making the necessary calculation. “Sleeping quietly” makes allowance for no movement save that of respiration; any undue restlessness will call for an increase in the above allowance.
“Sitting at rest” includes the time spent at meals, sitting in class room, ward office, studying or reading. It does not include much walking about the room, rising frequently, or nervous restlessness.
“Light exercise” includes all light house work, running an ordinary sewing machine, walking about office or ward, (receiving ward included). It does not include washing, sweeping or scrubbing.
“Active exercise” includes washing, sweeping, scrubbing, general house work, carpentry, and such sports as tennis, basket ball, and ordinary gymnasium work.
“Severe exercise” includes road workers (working with pick and shovel) fast running, baseball, football, and swimming.
“Very severe exercise” includes the work done by miners, handling of freight, and lumbermen, especially those working in extreme cold, where the severe cold makes extra demands on the fuel supply. By making use of the averages just mentioned it should be a simple matter to calculate the food requirements of any normal individual. It is necessary to know the weight of the person in question, and the manner in which the twenty-four hours are spent, and, in the case of elderly individuals, make the reductions believed to be necessary for health.
Method of Using the Tables.—Let us take a nurse in training for this purpose. Suppose the nurse weighs 110 pounds, and spends the twenty-four hours as follows,
| Sleeping | 8 hours |
| Sitting at meals | 2 hours |
| Studying | 2 hours |
| In class | 1 hour |
| On duty | 9 hours |
| Off duty (walking briskly) | 2 hours |
Her daily food requirements would probably be approximately 2,235 calories. This estimate would be increased, if she were obliged to do much heavy lifting, scrubbing of beds, or other duties requiring the expenditure of much effort. It would be decreased if the hours spent in study and class room work were increased and the hours on the ward shortened. The estimation may be made as follows,
| Sleeping 8 hrs. | 110 × 0.42 × 8 | = | 370.0 calories |
| Sitting at meals 2 hrs. | 110 × 0.65 × 2 | = | 143.0 calories |
| Sitting in class 1 hr. | 110 × 0.65 × 1 | = | 71.5 calories |
| Studying, 2 hrs. | 110 × 0.65 × 2 | = | 143.0 calories |
| On duty 9 hrs. | 110 × 1.10 × 9 | = | 1089.0 calories |
| Off duty (walking briskly) 2 hrs. | 110 × 1.90 × 2 | = | 418.0 calories |
| Total for day | 2234.5 calories | ||
This estimate may be made to suit any individual, the man in the office or the one working on the streets, the woman living at home or the one spending eight or ten hours scrubbing the floors of a great office building; it is simply a matter of adjusting the calories in the dietary to meet the requirements of body weight and muscular activity.
Energy Requirements for Children.—In estimating the energy needs of children, the above method is not satisfactory, since the storage of material for growth must be considered, as well as the activities of the body. The growth period includes the years from birth to the eighteenth year, after which time the food requirements of the body are made on a basis of weight and muscular activity, as in all adults. The table on the following page shows the food allowances made for healthy children; in the feeding of malnourished or underweight children, more food in proportion to age is given in order to overcome the handicap under which they are suffering.
Food Allowances for Healthy Children[23]
| Age | Calories per Day | |
| Years | Boys | Girls |
| Under 2 | 900-1200 | 900-1200 |
| 2-3 | 1000-1300 | 980-1280 |
| 3-4 | 1100-1400 | 1060-1360 |
| 4-5 | 1200-1500 | 1140-1440 |
| 5-6 | 1300-1600 | 1220-1520 |
| 6-7 | 1400-1700 | 1300-1600 |
| 7-8 | 1500-1800 | 1380-1680 |
| 8-9 | 1600-1900 | 1460-1760 |
| 9-10 | 1700-2000 | 1550-1850 |
| 10-11 | 1900-2200 | 1650-1950 |
| 11-12 | 2100-2400 | 1750-2050 |
| 12-13 | 2300-2700 | 1850-2150 |
| 13-14 | 2500-2900 | 1950-2250 |
| 14-15 | 2600-3100 | 2050-2350 |
| 15-16 | 2700-3300 | 2150-2450 |
| 16-17 | 2700-3400 | 2250-2500 |
Calories per Pound of Body Weight per Day.[24]
| Years | Calories per pound, per day |
| Under 1 year | 45 |
| 1-2 | 40-43 |
| 3-4 | 37-40 |
| 4-5 | 37-40 |
| 5-6 | 35-37 |
| 6-7 | 34-35 |
| 7-8 | 32-34 |
| 8-9 | 30-35 |
| 9-10 | 30-35 |
| 10-11 | 28-32 |
| 11-12 | 28-32 |
| 12-13 | 28-32 |
| 13-14 | 25-30 |
| 14-15 | 20-25 |
| 15-16 | 20-25 |
| 16-17 | 20-25 |
After which time the food requirements are based on degree of muscular activity, boys and girls of seventeen years and over requiring as much food as men and women.
Children, like adults, differ in degrees of activity; that is, one child may be very active, running and playing more strenuously than another. Hence a margin of safety must
be allowed to cover the energy expenditures of the more active child, to safeguard it against becoming malnourished.
To facilitate the computation of the food requirements of children a schedule showing the number of calories per pound of body per day is included on opposite page.
The food requirements are such as to allow of a steady increase in the weight and stature of the child; the rate of gain for normal children should be as follows:
Average Rate of Gain per Week, for Normal Children
| Age Boys | Average gain, Ounces | Age Girls | Average gain, Ounces |
| First year | 3½-4½ | First year | 3½-4½ |
| Second year | 2½-3 | Second year | 2½-3 |
| Third year | 1¾-2 | Third year | 1¾-2 |
| Fourth to eighth year (inclusive) | 1¼-1½ | Fourth to eighth year (inclusive) | 1¼-1½ |
| Ninth to eleventh year (inclusive) | 1¾-2 | Ninth to twelfth year (inclusive) | 1¾-2¼ |
| Twelfth to thirteenth year (inclusive) | 2¾-3 | Thirteenth to fifteenth year (inclusive) | 2¾-3¼ |
| Fourteenth to sixteenth year (inclusive) | 3-4 | Sixteenth and seventeenth year (inclusive) | 1-2 |
The averages just given are for healthy children; those who are underweight for their age and height should show a more rapid increase in weight with an increased food allowance. It must also be remembered that a simple gain in weight is not sufficient evidence of a child’s normality; a freedom from gastro-intestinal disturbances, and a resistance to disease, are equally essential.
There have been tables arranged to show the proper weight for height for boys and girls of different ages (see [appendix]). These are valuable since, by their use, attention is called to the child who is not up to the average. Medical examination of such children frequently shows reason for their underweight, and measures may be instituted which may save the child from a lifetime of poor health.
Dr. Pirquet has arranged a scale (Pelidisi Chart) showing the state of nutrition in children, based upon the sitting height (in centimeters), to weight (in kilograms). See [appendix].