Most people do not exercise to achieve a greater degree of physical well-being, which is what all doctors and professionals will tell you: physical activity is essential for a healthy lifestyle. A healthy lifestyle means combining physical activity and a balanced and nutritious diet to achieve greater psycho-physical well-being.
And this is where the donkey falls. Most people do physical activity to lose weight or shape their body (lose weight and tone), with the result that, when they do not reach the goals they have set, they abandon everything and goodnight to the bucket. I have been going to gyms and the fitness environment for a few years, so in this article I want to answer a few questions related to physical activity.
Reading it will save you a lot of time and not make the wrong choices.

I DO PHYSICAL ACTIVITY TO LOSE LOSS

1) Why do I not lose weight while exercising?
There are two ways to lose weight by exercising: the first is by doing activities that burn a lot of calories, cardio or aerobic. This allows you to create a calorie deficit with respect to what you eat, as long as you don’t eat more, of course. Pros: You burn a lot of calories. Cons (= disadvantages): the metabolism adapts to the expenditure, increases nervous hunger, the exhausting work of just cardio reduces lean mass, worsens the hormonal balance (training hypothyroidism), slows down the metabolism because it increases physical stress. The result is that the balance goes down, but the physical condition worsens . This of course if we only do cardio or aerobics and if we do this activity every day for hours.

I have been making this mistake for about ten or twenty years of my life. I used to do exercise bikes and treadmills for six or eight hours a day, every day. Stepper four hours a day. Nothing more wrong. 
The second way is to reduce fat mass  by promoting lean growth. Put simply: do weights. Big beautiful. This causes you to gain muscle mass, and the scales go up. Over time, fat mass decreases, but without dietary cycling (periods when you eat more / periods when you eat less, all followed by a sports nutritionist) , fat reduction times are long.. Also, if your goal is to build muscle, you can’t stay on a strict low calorie diet, or you go back to the big mistake of case one, that of a lot of cardio. The body catabolizes, the metabolism suffers.
The third way is the one I recommend: doing both activities, obviously without staying there for hours.