Calories

    The body's most basic requirement is for energy and vigor.  To receive energy, the body needs food as a fuel, and oxygen to burn it.  The amount of energy that foods can produce is measured in units called calories.  A food calorie, or kilocalorie, is the degree of heat needed to raise the temperature of one kilogram (2.2 pounds) of water one degree of Celsius.
 
 

    The body changes the calories that are in food into energy, which is essential for every act from blinking your eyes to running a race.  Energy is also used for the growing process, for healing damaged cells, and for regulating body systems.

    The number of calories the body requires each day depends on how much energy a person's body has.  An active child can need more calories than a grown-up who works at a desk.  The body needs more calories in colder weather to stay at an even and steady temperature.
 
 

    If a person eats more food then the body needs, the extra calories are converted to fat.  This causes weight gain.  One pound (0.5 kilograms) of stored fat contains about 3,500 calories.  The best way to lose fat is by eating less of high calorie foods and getting more exercise. For most people a safe limit for losing weight is two pounds a week.  When you're dieting you should get an "O.K." from your doctor.  So called "quick and easy" diets are only fads.  Most diets are unbalanced.  The more unbalanced, the more harmful it is.