I've been a dietitian for 20 years (not nutritionist, no degree for this, anyone can call themselves a nutritionist...stepping off soapbox now). Some good points made already, some not so good ones. DON"T MAKE THIS HARDER THAN IT IS! Weight loss is nothing more than a numbers game. If you burn more than you eat, you'll lose weight. Eat more than you need, NO MATTER WHAT FOOD IT IS, and you'll gain weight. That's the basics.
Now, performance eating is the next step. It's a combo of carbs (your body's primary fuel source), protein and fat. Nothing is forbidden, nothing is bad, it's fitting it all in using the right portions. You'll burn more calories on your skiing days than you will on your non-skiing days so you'll have to take that into account. Protein is great but if you aren't getting carbs, you're screwed when you latch onto the rope. You gotta have energy for this. Don't avoid fat altogether either. It's got some essential vitamins in it and is used for some hormones etc. It's also VERY filling.
Just off the top of my head, to lose gradually and not starve, on ski days right around 2500 calories (130 grams protein, 350 grams carbs and 60-70 grams fat,). These are "targets". Don't go freaking out trying to hit every one, every day! Give yourself some leeway. This is a long term project. On non-ski days/rest days, right around 1900-2000 calories.
@skiboyny hit it right on the head; read labels, weigh foods and measure foods and keep track on something like fitday or myfitnesspal. That's probably the biggest thing I notice is people in general have no idea how much food they are putting in their bodies. Sounds like you've probably already got this point down.
PM me for anything more specific you need. I'll help any way I can. I've never ski'd the course YET so I sure won't be giving any ski advice! Good luck with the food!