Before I went to college I became really focused in bodybuilding. I went from 140ish to 173 pounds. I am 5'9 and was sitting around 6% bodyfat. Once I went back to school I couldn't find the time, but my new years resolution is to regain the look I once had, and hopefully compete in an amateur provincial competition in the near future. Not entirely focused on the merits of this thread, but the overall benefits are the same.
I found a tape measure much more beneficial than a scale. Since muscle mass is denser than fat, you will see more noticble change in your measurements, than in pounds off the scale.
Some specific bow shooting exercises I would focus on would be push-ups and dips for the chest, lying lateral raises,and front raises, paired with dumbell presses for the shoulders, upright rows and shrugs for the trapezius, and bentover rows, and FOCUSED deadlifts for the back. Add in some cardio (if you really want), and a few hindu squats or pistols for the legs and you'll be set.
Proper diet will absolutly make or break your success. Do all the reps you want, if your sucking back twinkies, it will all be for not! Proper rest, and recuperation is essential, work out every other day, and listen to your body when you are tired. Drink a ton of water, and don't underestimate the benefits of nutritional vitamins and supplements. A good multi-vitamin, and an amino acid supplement such as pure glutamine are well worth the cost. Mix up your routines, have fun , and never stretch cold muscles! In fact, stretch AFTER the workout, rather than before. You can stretch during, but it is essential to warm the muscles up BEFORE stretching to avoid injury, 5-8 minutes of light cardio, a few push ups/pull ups etc is all that is needed to warm the muscles before stretching. Still a good idea to stretch after a workout though.