Deep breathing meditation gets more oxygen into the body. This has many benefits. I lost weight doing only deep breathing meditation. It also makes you more relaxed and is excellent for the brain (of course). When you exercise you are doing the same thing, delivering more oxygen through the body, well, aerobics, because as far as I know, I did not gain any muscle mass. Many people are shallow breathers and this is not good. I am one of them, so deep breathing was excellent for me to do and learn how to adjust my breathing throughout the day to take in more oxygen.