Calories: Definition, Purpose & Total Count

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  • 0:02 Calories
  • 1:49 EER
  • 3:07 AMDRs
  • 4:26 Lesson Summary
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Lesson Transcript
Instructor: Rebecca Gillaspy

Dr. Gillaspy has taught health science at University of Phoenix and Ashford University and has a degree from Palmer College of Chiropractic.

A calorie is a unit of measurement used to express energy. There are three nutrients that provide the body with calories: carbohydrates, proteins and fats. Learn about these macronutrients and recommendations for total energy intake: EER and AMDRs.


Calories tend to get a bad rap because of their association with the obesity epidemic. Yet calories are vital because there are a number of necessary metabolic processes, such as breathing and maintaining a constant body temperature, that require calories for energy. In fact, if we had to narrow down the purpose of calories, we would say that calories provide energy. And we can define a calorie as a unit of measurement used to express energy.

Calories come from nutrients, which are the components of foods that we need for survival and growth. However, there are only three nutrients that provide calories. Do you know what they are? I'll give you a hint. One of them is found in abundance in a piece of bread. Another is found in a piece of chicken and the other makes up a stick of butter.

I wonder if you guessed correctly by saying the three nutrients that contain calories are carbohydrates, proteins and fats. Together these three nutrients are called macronutrients. There are also two micronutrients, which are vitamins and minerals, and water is considered a nutrient as well. However, taking a vitamin pill and washing it down with a glass of water would not provide the body with any calories.

It is interesting to note that the three energy-yielding nutrients - fats, proteins and carbohydrates - do not all supply the same amount of calories per unit of weight. We see that a gram of fat provides 9 calories, while a gram of protein provides 4 calories, which is the same for carbs, as a gram of carbohydrate provides 4 calories. It's fairly easy to recall that fats provide the most calories per gram if you think of fat as the nutrient that makes you fat, although this is not really how it works.

Estimated Energy Requirement (EER)

The federal government has developed recommendations for energy intake to help you stay healthy and maintain a healthy weight. The Estimated Energy Requirement (EER) provides us an estimate of the total calorie count needed to maintain energy balance. So you can see that this term's name does a pretty good job of explaining what it is. It is truly an estimate of the amount of energy you require to get through your day.

It's based on calculations that account for factors unique to you, including your age, gender, height, weight and physical activity level. As these factors change, so does your EER. For example, if you start a running program, then you will require more energy from calories. These are only estimates, and each individual will be different; because of this, the federal government and other reputable sources have made online tools and EER calculators available to help you estimate your daily energy needs. But, to give you an idea, estimates provided by the Dietary Guidelines for Americans place the ranges from 1,600 to 2,400 calories per day for adult women and 2,000 to 3,000 calories per day for adult men depending on age and physical activity level.

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