Here are definitions of energy and calories out of my nutrition textbook from my foods and nutrition college course. When I took the course over 15 years ago, the textbook was in its 7th edition. Now, it's in its 12th edition. I own both the 7th and 12th editions, so I'm listing the most recent.
- Energy - the capacity to do work. The energy in food is chemical energy; it can be converted to mechanical, electrical, thermal, or other forms of energy in the body. Food energy is measured in calories.
- Calories - units of energy. In nutrition science, the unit used to measure the energy is a kilocalorie (kcal or Calorie): it is the amount of heat energy necessary to raise the temperature of a kilogram of water 1 degree Celsius.
There are three basic building blocks of food energy: fat, carbohydrate, protein. Each of these has an energy value:
- fat has 9 kcals/g
- carbohydrate has 4 kcals/g
- protein has 4 kcals/g
To recap, we take in energy by eating food and drinking liquids (beverages).
So, what is energy output? Well, our body uses up this energy kinda-like fuel. In order for our bodies to work, they need fuel. So, what kind of work would this be? Well, first of all, there is the metabolic functioning of the body. Metabolic functions are the things our cells do. The cells in our body are super busy making hair, skin, nails, just to name a few. They drive the functions of our organs and systems. All these basic functions our bodies do are work, and work takes energy. Even while we are sleeping, our cells, organs, and systems are working. Secondly, our brains use energy. Thinking, reading, writing, making decisions, and learning new things all take energy. Thirdly, physical work takes energy. Any physical work at all: walking, washing dishes, raking leaves, shoveling snow, working out at the gym, stretching. All these physical activities burn calories. The calories burned or that get used up vary depending on the intensity of the activity, how much you weigh, and an individuals metabolism. We are all different in many ways, but averages can be taken to figure out the approximate amount of calories per particular body weight (See chart of activities and calories burned for 1 hour at the end of this post).
So, to recap this section, energy output is every body function including brain function and activity, and every physical activity from typing to running marathons.
So, now what? Well, the figure below shows how it really works. The number of calories are just to show how the math works and have nothing to do with real calories consumed or expended.
You don't have to change everything all at once, just make small changes that seem like the better choices. And the more you do this, the easier it becomes for you to make these changes. Then, a month or two goes by and you can make a couple of more changes.
Below, you'll find activities and the calories you can burn in one hour doing those activities. You don't have to do this everyday either. Just pick one day a week that you can be active and slowly add from there. More information to come in Part 2.