Stay safe, eat a whole box of mac and cheese every day

So I was watching a special episode of this show called Top Gear the other day where they raced a dog sled against a super-modified Toyota Hilux all the way to the north pole. At one point during the show, one of the hosts mentioned that he had heard from some expert that if you're trying to survive in a harsh environment like the arctic, you have to eat around 5000 calories every day. That's almost as much as some heavyweight fighters and bodybuilders. I've been on long distance hiking/camping trips before, and we've eaten tons of high density food in a situation like that, but what about people that ski every day? 

I don't live at a mountain yet full-time, so I really don't know what effects a sustained ski season has on your body when you're out there every day for 5 or 6 months. However, I do notice that when I'm on a trip for a week or so and we're hitting it open-to-close every day, I can eat a whole damn box of shells n' cheese for lunch because I'm so hungry, and that's on top of booze and my other meals/snacks that I take in every day. Despite this, I still feel like whatever fat is on my body just melts away. Being shredded is sweet, but I don't want to be as skinny as an emo kid. 

When I move out to Aspen next season, am I going to waste away if I don't upgrade to TWO boxes of mac for lunch?