A calorie isa measurement of energy or heat. One calorie is the amount of heat it takes to raise the temperature of one gram of water one degree Centigrade.
What does this have to do with food? Well, we eat food to supply us with energy, and so energy in foods is measured in calories. When foods are metabolized—that is, utilized—by being combined with oxygen in the body cells, they give off calories (energy). In measuring the energy value of food, we use the “large” or kilogram calorie, which equals one thousand regular calories.
Each type of food, as it “bums up,” furnishes a certain number of calories. For instance, one gram of protein furnishes four calories, but one gram of fat furnishes nine calories.
The amount of calories the body needs depends on the work the body is doing. A man who weighs about 68 kilograms needs only 1,680 calories per day— if he does nothing at all. If he does a little work, he may need about 3,360 calories per day. And if he does heavy work, he may need as much as 6,720 calories a day to keep the body functioning properly.
There are other factors that decide how many calories a person needs, such as age, sex, size, physical condition, and even climate. Suppose you take in more calories than you need? The body uses up what it needs and stores some of it away for future use. The body can store away about one-third of the amount it needs each day. The rest becomes fat! And that’s why it’s important to
“watch your calories.”