Aerobic exercise mainly consumes

Aerobic exercise mainly consumes a mixture of carbohydrates and fat. The energy supply ratio of the two will dynamically change with the intensity and duration of the exercise, as well as the athlete's daily diet and training basis. There is no absolute fixed formula of "burning only fat" or "burning sugar first and then fat".

A while ago, I led a novice fitness group to answer questions, and this question ranked among the top three in frequency:

“Did I just start burning fat after running for 20 minutes? ”

“Why does the bracelet show that fat accounts for 70% of the energy supply when walking quickly, but only 30% is left when running? Is running faster a waste of energy? ”

Now the fitness circle has actually been arguing about this matter for almost ten years, and both sides have their own reasons.

One group insists that "low-intensity steady-state aerobic is the ceiling for fat burning", saying that as long as the heart rate is kept within 50%-60% of the maximum heart rate, fat will account for the highest proportion of energy supply and the total amount of fat will be burned.； The other group does not look at the proportion of energy supply at all, but only calculates the total consumption - even if the proportion of high-intensity aerobic fat is only 30%, it can burn 600 kcal in one hour, which means that it also burns 180 kcal in fat. It is not much different from the situation where low-intensity aerobic fat burns 300 kcal in one hour, of which 210 kcal is fat. Coupled with the afterburning effect that energy will continue to be consumed after exercise, it is more cost-effective.

In fact, you can think of the body's energy supply system as the power supply combination of the community. Residents usually have low electricity load (such as low-intensity exercises such as walking and yin yoga), and mainly rely on photovoltaic power stations (fat) for energy, which are clean and have large reserves. Thermal power generation (glycogen) only needs to be set up to fill the gap.； If the entire community turns on air conditioning in the summer (such as running, running, Pamela and other medium-to-high-intensity sports), the output of photovoltaics cannot keep up with such urgent demand, and thermal power generation will have to be fully utilized. At this time, the proportion of photovoltaics will naturally drop, but the total power generation will actually increase.

And there really is no such thing as "only burn sugar in the first 20 minutes, and burn fat after 20 minutes." From the first second you move, the two energy supply systems are working at the same time, and the difference is nothing more than the proportion.

In the past two years, I also encountered the trap of extremely high heart rate. In order to get within the so-called "fat-burning heart rate zone", I raised my wrist every three minutes to look at the bracelet when I ran. Once my heart rate exceeded, I slowed down. After a month of struggling, my weight did not move at all. It was only later that I realized that I had to drink half a cup of soy milk with added sugar before every run. That little bit of free sugar was enough to burn me for 40 minutes, and I ended my exercise before the fat was even used up. It was strange that it was useful.

Later, I tried running in the morning on an empty stomach for three months, 40 minutes each time, with my heart rate controlled at about 65% of my maximum heart rate. I ate 1.8g of protein per kilogram of body weight every day. After three months, I lost 2% of my body fat and my muscle mass was not moved at all.； But my friend who ran with me didn’t pay attention to protein supplements. He only ate a vegetable bun after running every day. In one month, he lost 5kg in bench press weight, and he went to measure body fat and found that he lost 2 pounds in muscles. This is why fasting aerobics is so controversial now. It can indeed increase the proportion of fat energy supply in the early stage of exercise, but if you don’t pay attention to protein supplements, it is easy to lose muscle, and it is not suitable for people with hypoglycemia.

To be honest, there is really no need to worry about the details of the energy supply ratio on the bracelet. In the first place, exercise is for comfort. If you can spare 1 hour of exercise every day, but don’t like the feeling of being out of breath and unable to speak, then walk briskly, jog, or ride a bicycle slowly along the riverside. Listen to a podcast or catch up on a TV series while moving. It will be comfortable and you can persist. In the long run, the effect will not be bad at all. ； If you get home after get off work every day after 8 o'clock and can't squeeze in much time, then 20 minutes of high-intensity intervals will consume enough. It is better than lying on the sofa for half a day to read fitness information.

In the final analysis, the core of aerobic exercise is "movement". What you consume is really secondary. Exercise that makes you willing to persist is the best exercise for you.