Before spreading the myth that slow running or walking “burns” more fat than fast running or interval training, as well as the myth of spot reduction (exercise is not bodyline), let’s first understand what we mean by the phrase “burning fat.”
Fat burning occurs through the hydrolysis of triglycerides by lipases, resulting in the release of energy. Through the action of lipases, glycerol and fatty acids are produced. The fatty acids are broken down into acetyl-CoA through beta-oxidation. NADH is also produced during beta-oxidation. Beta-oxidation of fatty acids is the primary method of energy release from stored lipids. The enzymes involved in beta-oxidation are located in the mitochondria in animals and in peroxisomes in plants.
Now that we’ve set a foundation, let’s debunk the urban myths that have proliferated over the last decade and whose spread leads to misleading results.
Myth No. 1: When I run, I burn fat from my belly… It has never been possible, nor will it ever be, to choose which area of the body the fat will be drawn from to supply the energy needed (for example, with sweat belts, another marketing scam). Each person’s body is different, and the body will draw fat from where there are the most fat cells or where there is the highest concentration of carnitine. Nonetheless, the body will draw fat from all areas; it will just change the percentage distribution of the points from which the fat is drawn.
Myth No. 2: Slow running burns fat, but fast running does not: If we want to delve into the intricate paths of exercise physiology, we must understand that we always use all three energy substrates to supply the energy we need (ATP-Pcr, Glycolytic system, Beta-oxidation of fatty acids). What changes is the percentage participation of each. For example, in a 100-meter race, the ATP-Pc system will provide 95% of the energy needed, while the remaining 5% will be divided between the other two energy substrates. In contrast, in a marathon, these percentages are reversed. The intensity of the exercise, defined as 60-65% of maximum heart rate, is what stimulates the third system, responsible for fat burning. For a relatively experienced runner, this intensity might correspond to running at 12 km/h, primarily using beta-oxidation and burning a higher percentage of fat. (Remember, we never burn only fat, but we can maximize the percentage for the energy required by the exercise.)
Myth No. 3: If I sweat a lot, I burn a lot of fat… Here, simply ask yourself, why do you train rather than just sit in a sauna? Clearly, this is not true, unless you decide to wear a sweatshirt in the middle of summer, in which case you’ll end up with at least hyponatremia and dehydration.
Aris Myrkos PhD
Founder and Head Coach, sciencetraining.gr
Sports Scientist
