What does aerobic exercise consume first?

In fact, from the first second of aerobic exercise, glycogen, fat and a very small amount of protein will be used for energy at the same time. There is no clear demarcation between "consuming one type first and then burning the next". The saying "only sugar is consumed in the first 20 minutes and fat is burned after 20 minutes" that has been posted on the Internet for many years is actually a misunderstanding of the change in energy supply ratio.

Why is this statement so widely circulated? In fact, changes in the proportion of energy supply can easily give people the illusion of "staged switching". You can think of the human body's energy supply system as a double stove in the kitchen. One is a high-fire fast-frying stove that supplies glycogen energy, which produces energy quickly and has strong explosive power. The other is a low-fire and slow-simmering stove that supplies fat with high energy density but slow release speed. The two stoves start from high heat. I have been working since then, but in the early stages of exercise, the body needs to output energy quickly, and the stove is turned on more vigorously. The energy supply ratio of glycogen can reach more than 70%, and fat only accounts for 20-30%. Therefore, many people feel that the first 20 minutes of exercise are "useless for fat loss."

I also believed this when I first started running two years ago. I would not dare to stop until 20 minutes each time, for fear that all the previous running would be in vain. Later, after talking with the sports rehabilitation therapist on the team, I found out that when I started to run for 10 minutes and was coughing, I had already lost fat. It’s already being decomposed to provide energy, but it’s just a small amount. If you can’t find a whole time to exercise every day, walk two more stops to and from get off work and climb the stairs for 10 minutes. If you add up, you can save a lot of fat and burn it. There is no need to be tied to the “20 minutes” number.

Of course, not everyone's energy supply ratio changes in the same way. If you do low-intensity aerobics on an empty stomach, your glycogen reserves will be small, and the energy supply ratio of fat can rush to more than 40% at the beginning of exercise. This is the core reason why fasted aerobics has become popular for so many years, but the corresponding controversy is not small. Many researchers believe that fasted aerobics has a higher risk of muscle consumption, and is also prone to hypoglycemia and dizziness. There is no absolute right or wrong in the fitness circle. It all depends on the individual's body tolerance.

If it is low-intensity aerobic exercise that lasts for more than 1 hour, as glycogen reserves are gradually depleted, the energy supply ratio of fat can rise to 60% or even higher. At this time, the energy supply ratio of protein will also rise to about 10%. Therefore, after running a marathon or walking a long distance, don't just supplement sugar and water bananas. Eat some high-protein foods such as eggs and milk. This can reduce muscle loss and help you recover faster.