Is yoga very good for weight loss? or does it just mainly focus on flexibility and strength? I have been contemplating substituting yoga for one or two of my cardio sessions, is this a bad idea?
Depends on the type of yoga and how long you hold poses for. It also depends on your current routine/menu.
Typically yoga is NOT the same as a cardio session. But what kind of cardio session is it replacing? A low intensity walk session is comparable to a Hatha class.