Why does aerobic exercise cause weight gain?

Nowadays, many people are obese, so they exercise regularly, hoping to lose weight through exercise. However, many people will find a strange phenomenon after exercising. After doing aerobic exercise for a long time, they find that their weight has increased. It is really true that the more they lose weight, the fatter they get. So why do they gain weight during aerobic exercise?

Of course, we know that people who do not exercise will stimulate muscle growth after they start exercising, but with the exercise intensity of people who have just started exercising, the rate of muscle growth is actually very slow, and on average it may be only about 0.0X kilograms a day (of course, weight training will grow faster), which is obviously not the reason for the sudden weight gain in the short term. In fact, this phenomenon is mainly due to the body's adjustment of energy distribution. Fat is a very efficient form of stored energy, but breaking it down for use as an energy source is a slow process. Once the body needs to consume a large amount of energy in a short period of time, the rate of fat burning will not keep up, and energy must be supplied by carbohydrates that can be quickly broken down to produce ATP.

Therefore, regular exercise is a signal to the body, telling it:

"From now on, you may often have to consume a lot of energy in a short period of time, so you need to store more carbohydrates and less fat to avoid imbalance in energy supply."

The way to accumulate large amounts of carbohydrates in animals is through glycogen. After exercise consumes a large amount of glycogen, it stimulates muscle tissue to increase its absorption of nutrients (relatively speaking, fat cells absorb less), causing a large amount of glycogen to accumulate in muscle tissue (the more calories that turn into glycogen, the fewer calories that turn into fat). Many endurance athletes, in order to improve their athletic performance, will combine high-carbohydrate diets with training. In the best case, they can even increase glycogen by 2-3 times. Although glycogen breaks down quickly and can provide a lot of energy in a short period of time, its storage efficiency is not good (the opposite of fat). For every gram of glycogen synthesized by the body, 3 grams of water must be brought along. If the body increases its glycogen reserves by 400 grams to meet energy needs, it will be stored along with 1.2 kg of water and glycogen, for a total increase of 1.6 kg of weight. If this energy is stored in the form of fat instead of glycogen, it will only weigh about 200 grams.

Another less important factor is that people who have just started exercising often do not have enough muscle strength and endurance, so they are prone to delayed soreness the day after exercise. This is swelling and inflammation caused by slight damage to muscle fibers, which is a normal phenomenon. After recovery, muscle strength and endurance will increase. At this time, because muscle inflammation will be accompanied by edema, it will also cause a slight increase in weight.

From the reasons introduced above, we can see that when weight gain occurs during aerobic exercise, it is generally closely related to physical fitness. In addition, some people increase their food intake and gain weight after exercise. When weight gain occurs after aerobic exercise, you should adjust your exercise plan in time.