Greg –
You make an excellent point about the calorie cushion you enjoy when you first get out on the trail and how that cushion quickly dwindles. Does anyone know what the general rule of thumb is how long this cushion lasts?
As an example, I was fortunate to have the opportunity to do enjoy a long-distance hike. At first I couldn't believe how much my (skinnier) friends were eating on the trail. They were always stuffing food into their mouths. I badgered them for frequently stopping to eat. What a fool was I. It wasn't before to long that I had to increase my caloric intake just to keep up with them…As I shed pounds, my need to eat increased. And thus I was the one always stopping and slowing them down. We would notice that after eating a meal or two in town during a food stop, the next few days we would hike stronger just because of the infusion of calories.
I emphatically agree with your point about the elevation gain along the JMT. There is a graphic that shows the profile, and with the exception of the climb out of Yosemite Valley and up to Cathedral Pass (both stiff climbs), the post-Muir Ranch portion (soutbound) of the trail enjoy a large number of serious ascents over 12,000 ft+ passes. You will need to click on this elevation profile graphic to get it enlarged and then scroll to right or left (http://www.pcta.org/images/elevation_new.jpg)
Finally, a hiker gains rapidly gains elevation along the JMT. This will slow down most folks, and thus, the food requirement generally increases since the miles get only tougher.
Dirk