RE working had and calories
I'm a big fat guy now, but I remember one camping trip back when I was oh, 17 or so - we were not car camping etc, we were backpacking, and couldn't really afford freeze dried stuff, so it was store dry stuff, and cooking time - 2 week trip, and I'd say we averaged 2-3k elevation change a day, with 50+lb packs on - Hike 10-12 hours/day, with elevation changes, often bushwacking, and gad do you burn calories
I know every chance we had to make a side trip to get supplies, we did. The middle weekend, Mom and dad came up with like 10 lbs of lasagna, they ate one small piece each, and the 3 of us who were hiking at the reast, then asked for a lift into town to get some more food
I think the least any of us lost was 10 lbs, and I lost like 20, and I don't even want to KNOW how many calories/day I was eating - 3K was probably low