I run about 5% body fat and am considering an AT thru hike in 2013. I am aware of the large daily calorie expenditures and that many people lose weight. My initial thinking is that I haven't enough fat for a safe enough buffer to maintain my health while on the trail. Conversely, the added efficiency and required vigilance in maintaining nutrition and calories demanded of hiking with a leaner body composition may be a big advantage to happily covering ground. What do you think? Thanks