By Michael Ormsbee, PhD, Florida State University

Edited by Kate Findley and proofread by Angela Shoemaker, The Great Courses Daily

Burn calories while resting—sounds too good to be true, doesn’t it? Thankfully, it’s possible. Professor Ormsbee describes the relationship between calories and exercise.

Calories Aren’t the Enemy

Although it’s important to pay attention to caloric expenditure when it comes to body composition, don’t go overboard—you need calories to perform properly. Think of your body as a car. Your skeletal system is the car body, your muscles are the pistons, and your cardiorespiratory system is the engine. 

It’s great that you have a fine-looking car, but you need fuel, and that is what the metabolic system is for—converting ingested food into stored energy and then converting this energy into fuel to support body movements. The strongest muscles in the world or the most powerful heart in the world are completely useless without the metabolic system doing its job of fueling the body with the energy needed to perform.

Calories are essential—don’t treat them as the enemy. Food is fuel. Fuel your body properly for optimal body composition and performance in any aspect of your life—mental or physical. 

Fueling Workouts

For most of us, our main energy source during exercise comes in the form of muscle glycogen. Your body has plenty of fuel to perform most exercises—generally about two hours of moderate- to high-intensity exercise.

However, sometimes we do run out—which is part of the reason you see athletes collapse from time to time. Their bodies have run out of the ability to access and utilize fuel. 

Most runners have experienced a time when they’ve hit the wall or bonked during a long run. They have the mental fortitude to continue, but the body simply won’t run—and the body’s systems begin to shut down.

The body is absolutely remarkable at properly operating all of its intricate systems most of the time– from muscles to enzymes to atoms—in complete unison. It requires good-quality fuel, though. 

All calories are not created equal. It would not be logical to drink a six-pack of soda or to eat five cupcakes to fuel up before a morning run.

Still, you may be confused about what to eat and how often to eat. When it comes to exercise and energy expenditure, you may be wondering what the most effective workouts are to keep your weight under control. 

Caloric Expenditure and Exercise

Exercise increases your caloric expenditure above resting levels or your resting metabolic rate (RMR) based on how long and how intensely you exercise. Does this increase in metabolism last after you finish exercising? In other words, does this increase in caloric expenditure help you burn more calories throughout the day?

Research has shown that your energy expenditure, in fact, does remain elevated after cessation of exercise. It is important to note that the amount of elevation in metabolism is dependent primarily on the intensity of the exercise and, to a lesser degree, the duration of your exercise. 

For example, if you walk or jog for 30–60 minutes, you’ll likely return to a baseline of energy expenditure within an hour—and probably only burn 30 more calories during that hour than if you didn’t exercise. Ultimately, this afterburn won’t play a big additional role on your total daily energy expenditure. 

If you do a more highly intensive exercise, though, it may have a big impact on how many calories you burn throughout the day. What you do during exercise makes a difference in your resting metabolic rate.

Let’s look at an elite marathon runner who runs at an extremely high intensity for over two hours. Her post-exercise energy expenditure will remain elevated for an extended period of time and could potentially play a large role in her total daily calorie expenditure.

Overall, whether you’ll get a lasting higher RMR after exercise is primarily a factor of intensity and to a lesser extent duration. A similar concept applies to lifting weights. 

Plenty of research has shown that vigorous weight training can increase your metabolic rate for hours after exercise. However, the average person who takes long breaks between sets will likely not see a large enough elevation to play a significant role on total daily energy expenditure. Overall, you can potentially increase your caloric expenditure once you finish exercise, but you have to work out hard and long enough to reap the beneficial effects. 

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.

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.