How was your body fat determined? I have a hard time believing that 13.1% figure, unless you are very heavily muscled, and have very little fat around your abdomen (less than 1").

If your body fat is actually that low, then you would have to lose muscle mass to lose that much weight. Pro cyclists routinely do this to increase their power-to-weight ratio (they have no arms and no chest muscles)...but, most of us who aren't being paid to ride like to look a little more developed.

Another way of determining body fat percentage is available at this web site: http://www.he.net/%7Ezone/prothd2.html. It only requires two simple measurements, and uses formulas developed by the US Dept. of Defense. It's not as accurate as water weighing, but should be in the ballpark.

Your current Body Mass Index is 28.1 (based on weight and height). The somewhat controversial cutoff for "overweight" is 25, with 30 being the generally accepted cutoff for "obese". At 170, your BMI would be 24.7 - a very reasonable goal...and, you'll definitely be faster on the bike.