Exercise, or fitness, can be roughly divided into two categories: aerobic exercise and anaerobic exercise. Like the way you exercise now, it seems that you want to gain muscle, which should be considered anaerobic exercise. Aerobic exercise is basically to increase physical endurance and cardiopulmonary function, such as running and swimming. Anaerobic exercise mainly increases strength and muscle dimension. The functions of these two kinds of sports cannot be substituted for each other. It doesn't mean that as long as you exercise, all the functions of your body will be improved. No matter how hard you practice, you won't improve your endurance and heart and lungs. On the contrary, if you only practice aerobic exercise, your body may become thinner and thinner. Depending on your state, if you have no disease, there may be two reasons. First, you lack aerobic exercise and your physical function declines. Before practicing strength, you should do some aerobic exercise step by step to make your body gradually adapt to the state of exercise, and then start training. In addition, no matter how much you have practiced before, when you start to practice strength again, you must do it step by step, and you can't enter the maximum training volume in the first week or two. Second, dizziness may be hypoglycemia. Don't eat too much before training, but you should also eat something, such as bananas and sports drinks (sugary).

Besides, I think there is something wrong with your previous training methods. If you want to lose weight, you don't have enough exercise. Besides these, you need to add some aerobic exercise. If you want to gain muscle, then these methods are all wrong. When practicing the muscles of various parts, the weight of each group of exercises should make you do about 8- 12 times, each movement should be done in about 3 groups, and each exercise should be done in about 3-4 different movements. The next time you practice the same part, you should wait until your muscles are fully recovered, instead of practicing every day. Then slowly increase the weight, and the muscles begin to increase. In addition to training, there are two important factors in building muscles: nutrition and rest. During the training, you should eat more food, especially protein-rich food, and then pay attention to rest and don't do a lot of extra physical activities.

Although exercise is necessary for health, it is equally important to master the correct methods. Blind exercise will only backfire.