The Secret Behind What Happens to Fat When You Exercise

Very few people would question the dynamic benefits of exercise to improve health and wellness, but very few people know about the science behind what causes these beneficial health changes to our fat and muscles.

Exercise will both increase our calorie burn and our respiration rate, so it’s the best route to burning away the pounds!

A pound of fat weighs the same as a pound of muscle – one pound. The difference between the two, however, is that one pound of muscle takes up much less room than one pound of fat. So if you gain an extra 10 pounds of fat, it will increase your stomach size a bit. Ten pounds of muscle, gained through strength training, however, would certainly firm up your muscles, but not show a significant size increase.

The Role of Fat Cells

Our bodies have a certain number of fat cells. These are set for us at several points during our youth and will not change as we age. Fat cells will, however, increase or decrease in size depending on our nutrition and activity. It’s a matter of calorie balance. Fat cells will stay the same size if the calories we consume equal the calories we utilize each day. If you consume too many excess calories, the size of your fat cells will increase. If you burn extra calories through exercise, the size of the fat cells will decrease.

The puzzling question is what happens to the fat – where does it go?

The answer lies in our respiration. Yes, our breath and breathing is responsible for fat elimination, according to a 2014 study published in the British Medical Journal. Nearly 84% of fat molecules are exhaled as carbon dioxide. Another 16% leave the body through water, including sweat, tears, urine, and other liquids. Exercise will both increase our calorie burn and our respiration rate,  so it’s the best route to burning away the pounds!

Exercises for Burning Fat

The primary types of exercise that burn calories and fat are cardiovascular activities: walking, cycling, swimming, and jogging. This is because as you do these exercises, you breathe a lot and therefore exhale a lot of fat cells.

See our post Breathing for Better Exercise to better understand how to maximize the release of fat cells.

What Makes Your Muscles Grow

Skeletal muscle on the other hand is made up of fibers. Without stimulation, those fibers tend to stay the same. If you stimulate, or as I like to say “challenge” the muscle, the fibers will grow, become more powerful, and increase in size. For the muscle fibers to grow and improve in strength, they actually tear in a microscopic way when you train them. These tears are part of what causes muscle soreness after exercise.

Delayed Onset Muscle Soreness (DOMS)

As your body heals these tears, your muscle fibers become stronger. The more frequently you repeat this process, the more your muscles will improve in strength and size. You will typically begin to notice this type of soreness within 12-24 hours of exercise and it will last another day or two. If this soreness lasts longer than that, you might consider decreasing the intensity of your exercise. Of course there are other factors that influence our gains in strength and size such as nutrition, genetics, and the types of training we use. For more information on DOMS, I recommend this article from The American College Of Sports Medicine.

What results have you seen with increasing your muscle size and decreasing fat based on the type of breathing and training that you do?