Sedentary occupation and two hours' exercise increase man's daily food-need from 1850 calories to 2500 calories to main-tain repair and provide nutriment and body-heat.

(Specific facts on life-food are from Dr. Graham Lusk's "Fundamental Basis of Nutrition.")

The food-need of workers has been closely studied. It has been found that the amount of muscular effort exacted by different kinds of work requires differing quantities of food-energy.

For Occupational Energy-Requirement, see p. 222.

The quantity of energy-food (carbohydrates and fats) is the chief change work requires in diet. But in hard muscular labor a constant relatively high supply of building-food is necessary (protein, .25 lb. per day). This is not only for tissue-repair but also because protein facilitates utilization of all food eaten. The workers it is who need a liberal meat- and egg-supply.

Both sugar and fat can be digested in larger proportion by those at hard work than by others. The high heat of fat and the rapid heat-giving of sugar make these desirable work-foods. Those underfed in winter always consume sugar in abnormal quantity whenever it becomes available.

Starchy foods are work-foods of unique value, because starch gives sustaining energy - energy that lasts. As the amount of food of the work-diet should be large and the working body is active, food with little cellulose (woody fiber) is advisable. When it is present in large quantity it may hasten the food through the alimentary tract of those at hard work, before it has had time to be digested. Similarly the workers find white bread, not whole wheat, is the bread they should eat. Potatoes and rice have such fully available starch as to be most desirable work-foods. Their protein that is soluble also makes them valuable in work-diets.

Green vegetables and fruits are desirable in all diets and need to be obtainable by workers.

Much water and air in abundance are essential for the complete utilization of so much food as workers need. Time to masticate and digest food is a health-requirement for all that live.