Casey, a lot of the answers to your questions are given in this earlier post of mine on another thread.
http://www.backpackinglight.com/cgi-bin/backpackinglight/xdpy/forum_thread/13490/index.html?skip_to_post=99510#99510
I did put on 13 pounds over the Winter (Minnesota Winters are too cold for me to hike in, getting 50 below zero sometimes — I know some get out, but I'm not a native Minnesotan). My goal this year is to avoid putting the weight back on by doing weight lifting.
We had trouble eating all 3,000 calories but I always came close. Remember, I'm consuming calories from the body fat I burn, so I'm consuming about 6,500 calories a day (isn't a pound of fat 3500 calories?).
As for energy, I bring powdered energy drinks, the muscle recovery drink, and okay, I'll confess, even 1 or 2 NoDoz tabs throughout the hike to keep me going. It's hard work hauling a pack going up 2,000-3,000 feet a day (especially coming out of the Kern Canyon, going up over Kawheah Gap, or over TrailCrest Pass).
I follow Dr. Sears' Zone Diet which believes in providing the most energy for the least number of calories, which optimizes the body's production of Econosoids and optimizes the body's blood levels too. Simply speaking, it advocates maintaining 40 percent of calories from low-glycemic index carbs, 30 percent of calories from protein, and 30 percent of calories from healthy fats (and if possible with an optimal balance of essential fatty acids). I do bring along the ZoneLabs concentrated, pharmaceutical grade fish oil capsules on the hike which besides helping one zone, also reduces inflammation. His web site is http://www.zonediet.com. It's a little hard being zone-perfect on a hike but I try to maintain the balance as best as can be.
ps. The Zone diet is one that strives for one that optimizes the burning of excess body fat too. But one key part of the zone diet is exercise and the reason I do so good on the hike with the Zone Diet is that I'm doing my most amount of exercising while hiking (isn't that strange ).