What is a Calorie?

photo credit: The Vista Dome

We hear the word “calorie” used all the time when we discuss diets. You eat so many calories, burn off a number of calories in exercise, restrict calories to lose weight; but what exactly is a calorie? Technically, it’s a measure of heat, or energy. A calorie (actually a kilocalorie) is the amount of energy required to raise a kilogram of water one degree Celsius. The number of calories provided by a food is determined by using equipment called a bomb calorimeter to burn the food and measure the energy it yields. We obtain our energy from food, and we burn it through activity and daily body functions; or–if we have enough and don’t need any more at the time–we store it as fat. Later, our body cells can access the fat and receive calories from it.

In food we receive calories from carbohydrates, protein, and fats. These all contain Carbon, Hydrogen, and Oxygen (protein contains nitrogen as well). These compounds go through a series of biochemical reactions in the cells to yield energy. The energy is used to power movements in our body, including breathing, our heartbeat, digestive processes and other functions that take place 24 hours each day, as well as walking and other exercises. At the end of the chemical reactions there is always some carbon remaining. The body rids of it by attaching to oxygen which we have breathed in. As a result, we breathe out CO2. While you probably remember learning in fifth grade that we breathe in oxygen and breathe out CO2, you probably never stopped to wonder where this carbon atom came from …. so now you know!

When you exercise you notice that your breath becomes deeper and more rapid. This is because you are generating heat (which is why you sweat), using energy (which has come from food you’ve eaten), and breathing off more CO2.

How do vitamins work into the equation? A common misconception is that we get energy from vitamins and this is not the case. Many vitamins are used as “coenzymes”, or catalysts, in the energy-yielding reactions. Without vitamins your body cannot obtain the calories from the foods you eat. But taking more vitamins won’t give you more energy any sooner than putting extra gas in your car will make your car go faster!

The key to energy balance is taking note of the energy (calories) you consume from your diet and working it off with some extra activity on days you eat a bit more than usual. So keep up the exercise, eat a variety of nutritious foods and limit extra fats and sweets, and you’ll be good to go!

Written by Laurie Beebe

About The Author: Laurie Beebe has been a registered dietitian for 25 years and is certified in adult weight management. Laurie currently serves as a diet coach and life coach at www.mycoachlaurie.com

Related posts:

1. What’s In A Calorie?
2. How Does The Calorie Calculator Work?
3. Why Very Low Calorie Diets are a Very Bad Idea