No, muscle training and fitness can be done at the same time. You can drink muscle-building powder before and after fitness, and then eat pasta. You need to provide a lot of carbohydrates. Thin people need energy. There is no need to drink protein powder. You can also eat eggs and milk. Stick to exercise, mainly anaerobic, and running for 10 minutes is enough. Just to promote blood circulation, I weigh more than 5 kg a month according to the above practice.