ATP: The Currency That Keeps Our Body Running

How Bioenergetics Fuels Your Body

By Michael Ormsbee, PhDFlorida State University
Edited by Kate Findley and proofread by Angela Shoemaker, The Great Courses Daily

Most people think that energy is something you get from coffee or an energy drink. However, bioenergetics is much more than that. Michael Ormsbee, Ph.D., explains how ATP, at the core of bioenergetics, fuels everything from digestion to muscular contractions.

Healthy woman running in park
Adenosine triphosphate (ATP) turns the food we eat into a usable form of energy for our body processes to function. Photo by Daxiao Productions / Shutterstock

ATP and Bioenergetics

How do we produce energy from the food we eat, and which food choices are best based on our activity level? Bioenergetics is the process of converting the compounds of the foods we eat, like carbohydrates, fats, and proteins, into a usable form of energy called adenosine triphosphate, better known as ATP.

Bioenergetics relates directly to your metabolism, and metabolism is the sum of all the energy transformations that occur in your body. This could be anything from activating certain proteins to helping your immune system to function properly. These processes all require energy.

We produce energy by converting the food we eat into ATP. ATP is often called the energy currency of the body because in a sense we pay for all of our biological actions with ATP. 

Food is eaten and eventually converted into ATP, carbon dioxide, and water. ATP is used to produce work for all of your metabolic needs and daily activities. Heat is also produced in the process of making energy. 

Essentially, you have changed the chemical composition of the food you eat into other forms of usable energy and heat. This follows what is known as the first law of thermodynamics, which states that energy is neither created nor destroyed, but only changed in form.

Thus, ATP is stored chemical energy that links the energy-producing and energy-requiring functions within all of our cells. This energy fuels all forms of biological work: digestion and absorption, nerve transmission, blood circulating through your body, and muscular contractions.

Our Energy Systems

How do we make and replace our stores of ATP? We have three energy systems to accomplish this. In all three systems, a phosphate group is added to adenosine diphosphate, or ADP. Then, a process called phosphorylation ultimately creates adenosine triphosphate, or ATP. 

This means that phosphate is added to ADP, and then it’s stored as ATP until the energy in ATP is needed for activities like walking up the stairs, picking up a box, or exercising.

Each energy system has a specific role and works at the highest rate based on how hard or how intense you are working. Each system has a different way of providing ATP, but it is important to realize that they are used on a continuum, and they do overlap quite a bit.

In addition, certain parts of each of the three energy systems can also work to provide ATP in the other two energy systems. While this may sound confusing and problematic, it is actually another way of saying that you get all of the ATP out of whatever it is that you are doing and whatever fuel source—carbohydrates, fats, or proteins—that you are using to provide the energy.

By understanding these three energy systems, what you will gain is the ability to decide what to eat, or what certain nutrients may be best to support specific activities.

If you are doing something that uses more carbohydrates to produce ATP, then you will know what to eat to optimize not only your performance but also your body composition. On the other hand, if you are doing something in your daily routine that burns more fat for ATP or energy production, then there is less need to eat carbohydrates at that time. 

This allows you to better understand what you should eat to optimize energy production, limit storing excess fat, and improve success for fat loss.

This article was edited by Kate Findley, Writer for The Great Courses Daily, and proofread by Angela Shoemaker, Proofreader and Copy Editor for The Great Courses Daily.
Dr. Ormsbee is an Associate Professor in the Department of Nutrition, Food, and Exercise Sciences and Interim Director of the Institute of Sports Sciences and Medicine in the College of Human Sciences at Florida State University.

Michael Ormsbee is an Associate Professor in the Department of Nutrition, Food, and Exercise Sciences and Interim Director of the Institute of Sports Sciences and Medicine in the College of Human Sciences at Florida State University. He received his MS in Exercise Physiology from South Dakota State University and his PhD in Bioenergetics from East Carolina University.

About Kate Findley 232 Articles
Kate is a writer, novelist, and blogger living in Los Angeles. She has been writing for The Great Courses since 2017. It incorporates her two favorite things: writing and learning.