A calorie is a unit of measurement, and is commonly used to describe the amount of energy that is present in the foods that we eat. A single calorie is the precise amount of energy that it takes to raise the temperature of a cubic centimeter of plain water by a single degree (centigrade). http://www.nutritiondata.com/help/glossary#C

Calories are used by the body to function, and we need calories not only to perform everyday activities such as walking and lifting, but also to be able to live at all. Calories are what feed the body and allow our organs to go about their necessary tasks. So, while calories may have a nasty reputation among those attempting to lose weight, they are actually vital to us as human beings. However, consuming too many calories will result in weight gain, as the body will store any calories that go unused in the form of fat.

There are only 4 types if substances that contain calories. These are proteins, carbohydrates, fats and alcohol. Protein and carbohydrates each contain 4 calories per gram, while fat contains 9 calories per gram and alcohol contains 7.http://www.nutristrategy.com/nutrition/calories.htm It is recommended that 10 to 35 percent of calories consumed per day come from protein,http://www.cdc.gov/nutrition/everyone/basics/protein.html 45 to 65 percent come from carbohydrates,http://www.cdc.gov/nutrition/everyone/basics/carbs.html and 20 to 35 percent come from fats.http://www.cdc.gov/nutrition/everyone/basics/fat/index.html There is no recommended intake of calories from alcohol.

The advice in this guide is for informational purposes only, and should not be used as a substitute for professional medical advice. Please consult a doctor before using any of the methods described here.