First of all, I know that the essence of weight loss is to consume more calories than you take in.
But I have found that after a period of aerobic exercise, you will enter a plateau, or use whatever garmin or intervals.icu analysis platform, if you need to maintain positive exercise gains all the time, you need to keep increasing the intensity or volume of exercise, which means that there will come a time when excessive exercise will break your body.
Especially recently I have seen former Tour de France champions, now that they have become older, their bodies have also become fatter, I think one is a matter of age, and the other is that after retiring, they cannot maintain the amount of training as a professional. In addition, some friends have been training for a long time, but after marriage or after having children, the amount of exercise is extremely reduced, for example, in the past can guarantee 8 hours of training a week, may now only 2 hours, I can see the obvious changes in their body shape 
I was told by my coach to do more strength training, after the muscle increases, it will be similar to the body’s metabolism rises, so the daily calorie consumption will also increase a lot, but it is very difficult to maintain the muscle, requiring a perfect diet and sleep.
Overall, it’s really hard to stay in good shape over the course of a person’s lifetime. I don’t know if you guys have any good advice or point out where my problems lie. Thanks in advance!
You’ve pretty much described exactly why fad diet and exercise marketing works. So many people are looking for “the solution”, when in reality we are all very different and have very different genes. Some people can do very little and appear extremely fit. Others can work incredibly hard and see very little gain. Especially if the sport they love isn’t the one they’re genetically geared toward.
I suspect the best overall fitness health for most of us comes from an extremely clean diet and varying exercise so that we’re a strong overall athlete but maybe not exceptional at any one sport. I just enjoy cycling too much to reduce it in order to have more time for other sports that I enjoy less. As I age, my personal philosophy becomes much more about doing what you love and having great mental health.
If you understand the basic of weight loss as us say. It shouldn’t be to hard to figure out why people who reduce exercise gain body weight. They’re probably eating the same as when they were doing more exercise.
It perfectly possible to maintain weight while not working out at all. You probably will change in body composition without exercise but your weight can maintain the same. Just have to make sure you adjust your diet to the lack of exercise.
Oh yes, genes play a role in determining, I’ve seen too many people, even without exercise, are very thin, especially Asian women, they do not diet, just simply grow fat , there is an argument that poor digestion, eating will not absorb too much energy, perhaps not suitable for ancient hunting life, but in modern life, does not require the body to reserve too much energy, which is also fantastic