This has something to do with your stomach. You may feel that you have been exercising for so long, but you can't lose weight or even gain weight. This is because you burn fat during exercise to lose weight, but when you eat, you don't feel like eating too much, just eat enough. In fact, you consume more energy than your body needs, which causes the excess energy to be converted into fat, so you can't lose weight or even gain a lot of weight.