Edited by Kate Findley, The Great Courses Daily
Do women or men burn more fat while exercising? Dr. Ormsbee examines the evidence and the implications.
Gender Differences in Fat-Burning
When it comes to fat burning, studies now reveal a difference between how men and women burn fat. This was not always the case, though. Early studies of sex differences in fat use during exercise were conducted during the late 1970s and early 1980s.
Men and women were asked to run between 65 and 70 percent of their maximum intensity, and repeatedly fat use was not shown to be different between men and women when running at a set percent of their maximum.
In follow-up work, though, another study tracked the number of miles that the men and women ran per week, their years of exercise training, and their relative ability to use oxygen during exercise. Using this advanced design, some differences were found.
When the research participants ran at 63 percent of their maximum on the treadmill for 90 minutes, the women used significantly more fat than men during the exercise when matched for the different variables of training experience and muscle mass.
Also, there weren’t significant differences in blood levels of free fatty acids between men and women. This was all despite women having significantly higher blood glucose levels throughout the exercise session.
Others looked into 14 untrained, 14 moderately trained, and 14 endurance trained men and women before and after cycling at 60 percent of their maximal oxygen consumption for 90 minutes. The researchers found that in all three training scenarios, only the women were able to significantly utilize the fat stored in their muscle cells.
This shows that, when compared to men, women are better at using stored fat in their muscles for energy. Also, women were better able to store fat in their muscles than men prior to exercise starting.
Why Do Women Burn More?
Recently, it was also reported that fat use relative to body muscle mass was higher in women than in men. This is not entirely surprising because it is well established that, on average, women have a significantly higher percentage of the type of muscle fiber that is best used to burn fat as a fuel.
These fibers are known as type 1 oxidative muscle fibers. Women have about 68 percent of their muscle mass composed of type 1 fibers compared to men at about 55 percent, and these are the fibers that are used during slower and longer duration activities, the type of exercise that uses a lot of fat during the activity.
In general, women also tend to have a greater capillary density, higher percent of type 1 muscle fibers, and a higher fat oxidation than men during low- to moderate-intensity exercise.
You might ask, “Why do men seem to lose weight more quickly if women are actually better at using fat as a fuel?”
“The answer may be quite complicated but for simplicity sake, in my experience, men typically have more room to change, meaning they tend to start this journey at a higher fat mass than women in general,” Dr. Ormsbee said. “But let’s not go too far yet. All this means is that women and men alike need to exercise to use fat, and need to eat in the best possible way to support fat use and optimal health.”
Implications of Gender Studies
Overall, fat has many different valuable and necessary physiological roles in the human body. While fat has been maligned in the nutrition world for a long time, new evidence indicates that eating fat is actually beneficial for health and body composition, so long as: one, fat intake is not combined with a high sugar or refined carbohydrate intake; two, fat consumption is balanced between saturated fat, monounsaturated fat, and polyunsaturated fat; and three, total caloric intake remains aligned with your nutrition and body composition goals.
It is also clear that exercise of low and moderate intensity helps burn fat, but we also need to increase our overall calorie burn from exercise, too. That could occur with either more exercise or by including high-intensity exercise that really gets your blood pumping.
In the end, there may be small differences in how fat is burned and how much fat is stored between men and women, but you shouldn’t get too bogged down by that information. It is far better to stay focused on what you eat and how you choose to incorporate exercise into your life.
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.