I'm losing weight really well without exercise. To be honest I'm so tired all of the time and have frequent illnesses exercising really isn't something that's easy for me to do. When I'm done losing weight I want my arms and stomach tight, the rest of me right now is fine enough. If I start right now just doing weights with my arms and crunches daily would this ensure the tightning of my stomach and arms. Or is cardio necessary. I know cardio is good for health, I do. Just curious about making sure I don't end up with flabby skin.