I think that you should train aiming to increase your cardio-vascular capacity. Concentrate on getting your body into top shape. Don't try to become a body builder.
Just eat a healthy balanced diet and run, swim, cycle etc. If you train like a boxer, you would get into fantastic condition and it would do wonders for your overall health.
When you get older, you will realize that what really matters is having a healthy ticker. There are so many muscular athletes that die suddenly in their 40s and 50s. ( examples: Mike Webster, Reggie White. Steve Furness, Reggie Roby to name but a few )
Mad.