Your examples sound like fairly short-term biological responses to intense activity, which are likely different than long-term biological response to a signific

Your examples sound like fairly short-term biological responses to intense activity, which are likely different than long-term biological response to a significant increase in daily calorie expenditure. I've done a fair amount of wilderness backpacking. It's common to lose your appetite for the first few days due to the change in environment, schedule, activity, etc. But pretty quickly your body will realize this is going to keep happening and it's going to need to make up the extra 1000+ calories you're burning every day.