By Michael Ormsbee, PhD, Florida State University

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

Is swimming or running a better workout for burning fat? Also, do low-intensity workouts really burn more fat? Professor Ormsbee weighs in on these aerobic exercises.

Swimming or Running?

Swimming requires both upper and lower body muscle groups. However, it seems that for its equal intensity level of exercise, it expends fewer calories than either running or cycling. Why? Unfortunately, the answer is not that clear.

It is thought that the reduced energy expenditure for swimming is due to the body’s lower heart rate, although swimming has an equal intensity level of exercise as compared to running or cycling—and, typically, your body even feels like you have been working out at the same intensity level. The primary reason for the fewer calories expended is related to your body position during this type of exercise. 

In a more upright exercise like running or biking, the heart must work to a greater extent against gravity to return blood back to the heart. Think of the blood vessels in your body as a column, with the heart resting at the top. In relation to gravity, the larger the distance between the heart and the bottom of the column, the greater distance that must be overcome.

With upright exercise, your heart rate must be increased to overcome this greater vertical distance and assist with getting blood back to your heart. Swimming, however, requires you to lie flat, either supine or prone. 

In this position, the distance from the heart to the bottom of our column is considerably less; so, in terms of gravity, the blood travels back to the heart quite easily. This difference requires less work for the heart and produces a lower heart rate.

Colder Is Better

If you are an avid swimmer, though, don’t worry. Most times you swim in cool water, which may increase your total calorie burn. 

This is because you not only have to work hard just to swim, but you also have to keep your body temperature within a normal range. Similarly, this concept applies to running or cycling outside in the cold. 

Try to remember this the next time you are dreading your cold morning workouts. Maybe this knowledge will help motivate you a little to step outside into the frigid air.

If you’re not a runner, cyclist, or swimmer, aerobic classes like step or dance can be an effective way to burn fat, especially if they make your exercise more enjoyable for you. However, it is often more difficult to regulate the exercise intensity level during these types of classes, and it may be a less continuous form of exercise than some other choices, due to short breaks that are occasionally taken.

In general, running may actually be the most optimal aerobic exercise for fat loss. However, if you absolutely loathe running, or cannot run due to musculoskeletal limitations or injuries, every other form of movement is good and can result in significant improvements in your body composition, especially when paired with healthy nutritional choices and lifestyle habits.

Exercise Duration

The next aspect of aerobic exercise that you can manipulate to improve fat loss is the length of time you exercise or exercise duration. It is known that the length of time you exercise and the amount of calories you burn are directly and linearly related.

The longer you work, the more calories burned. This is pretty simple. How much time out of your day are you willing to give, though?

Sure, if you run for two hours, you will burn more calories than if you run for 45 minutes, resulting in more overall fat loss. However, this option may not be feasible or desirable. 

“I even see a lot of people who actually exercise for a long time but never change or improve,” Professor Ormsbee said. “This is because the exercise is not intense enough or their eating habits preclude the loss of fat.”

Intensity Matters

What if you could burn the same amount of calories in 45 minutes that you could over two hours by simply changing one thing about the way you exercise? You can—and that one thing is the intensity of your exercise.

If there is one thing that you take away from this article, it is that intensity is king when it comes to fat loss. Intensity is a measure of how hard you are working, which can come down to how you feel, or quantified by heart rate, exercise speed, or incline. 

A major misconception is the idea that low-intensity exercise is better for fat loss, often called the fat burn zone. Many exercise machines even have a button called “The Fat Burning Zone” for the low-intensity setting.

Unfortunately, high-intensity exercise is necessary for meaningful progress when it comes to body composition. The upside is that you don’t need to spend so much time exercising. More details will come in tomorrow’s article.

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.

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.