I am an insulin dependant dependant diabetic (IDDML) and am nearly 70years of age. In 2004 I rode the Northern Tier route, Seattle to Minneapolis, 2500 miles approx. I was nearly 69 then. I had trouble adjusting my diet for the first week and was running out of energy each afternoon. My average rate dropped from about 17mph in the mornings to 7-10 in the afternoons and I felt like quitting. I had good quality high cabo breakfasts but didn't feel like eating too much at braakfast or lunch. I was fit enough for the very hilly terraine. I ate a lot of high GL bars the second weekand after that. this and my increased fitness allowed me to average 19-20mph thereafter, except on some of the very steep hills. We rode 80mile days with some days over 100 miles. This is a long way around asking someone to tell me how I can prepare diet-wise before the ride starts and what to do to guard against a repeat of that first horrible week where every afternoon I desperately wanted to go home.