I second - both with my readings and my experiences - everything that loCarbJ mentioned. I would add one remark: not only the famous LC endurance athlete Mittleman, but many not "traditionally" LC Marthoner, Marathon trainer gives the SAME advice: to spare glycogen (for the last 6 miles sprint
) you have to train, to run on the race in/under your 80-83% MHRT zone.
When I started to run last January, I was fortunate enough being an unexperienced runner - means: my legs could not run faster than the "fat fule mode" zone. Some other disadvantage that was after all advantage: my stomach refused anything but water before run. So I started to run with emtpy stomach, and kept runnning up to 2 hours on no carb before or during traning. Deanne, I am absolutely sure you can do it. Without any problem.
BUT the problem starts somewhere 10-13 miles or 90-120 minutes. For us, runners without longer long distance past it is very hard to keep our heart rate under the 83-85% for 3-4 hours, simply because of the tiredness. See loCarbJ experience "around half time". Your heart rate starts to climb up mile after mile. Of course you can slow down - but this way you are increasing the time - making you more and more tired. Something else: the temperature. In 70% your heart rate can go up by 5- 10%, in 80F by 10-15%. If you do not start your long runs at 2AM - there is no way to avoid the heat.
Summa summarum: yes, you can run a long way without any carb. BUT because you have relatively short time (25 weeks) to train (your legs, heart, etc.), I would recommend to have a Plan B - just in case. For the 120 min+ runs. No, you do not need huge carb load, but you MIGHT need SOME carbs along the way.
No, this is not a treason against Atkins. One of Atkin's leading researcher doctor, an Ironman himself recommends GU for example during long endurance training.
Btw if you check your Marathon training plan (have you got some chart from TIT?), you will see that 90% of your shorter weekday and weekend long runs SHORTER than 2 hours. You need the "Plan B" only for the 8-10 12+ mile long runs.
I have excellent experience with the GU (20 carbs only) - one at every hour, if I run more than 2 hours.
After your first Marathon you will have plenty of time to train for a "no-carb" cross US run:-)
Go Girl, you can do it:-)))