Sir,
I'd applaud your getting in to cycling, but I'd caution you about diving in the deep end of the pool without a few swimming lessons first. Start slow like I did. I have lost about 25% of my body mass in a pleasurable year of cycling. I combined cycling with a low-carb diet very effectively. So you could take the weight off while learning the skills necessary first and getting fit before departing on a long tour. Buy a copy of Effective Cycling, by Forester and get a year or two under your belt before heading out on a journey that will require skill, patience and a much higher level of fitness and health than you currently maintain. Please take this advice as a honest answer to your honest and frank question. Best of luck.