at your height and weight, you don't stand a chance at losing 20lbs and still maintaining your strength. Losing 20lbs would probably make you a worse cyclist. fortunately, you are already height weight appropriate so you just need to train more and maybe lose a few lbs but nothing substantial. If your deadset on losing weight off your bike, losing weight off the wheels is where it's at but that can affect durability. IF you commute on clean, pothole free roads and don't lug heavy stuff in panniers than you can go with a lighter wheelset.