A calorie, also called a kilocalorie, is a unit of energy, much like a pound is a unit of weight. A calorie is the amount of energy needed to raise the temperature of 1 gram of water by 1 degree Celsius.
Daily Calories
The average American needs about 2,000 calories per day to maintain weight, but individual needs vary depending on body composition and activity level.
Energy
The number of calories in a meal is a measure of the stored energy in that food. Your body uses calories from food for running, thinking, breathing and every other bodily function.
Types of Fuel
Your body extracts three fuels from food: fats (containing 9 calories per gram) proteins and carbohydrates (4 calories per gram).
Burning Calories
Calories are burned when enzymes break down fat, protein and carbohydrates into fatty acids, amino acids and glucose, respectively. These fuel the body just as gasoline fuels an automobile.
Leftover Calories
Any calories that are consumed and not burned are stored as fat. Fat is your body's reserve energy bank. To burn off fat, you must provide your body with fewer calories than you will expend.
Nutrition Facts
Since 1990, all foods sold in the United States must list the caloric content on the packaging, making it easy to track your daily calorie consumption.
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