Without plenty of 'Real Whole Food' (not corporate processed junk food which is what most people are now loading up on) you're going to put on weight, (too much salt and sugar intake) lose focus, get dizzy and make clumsy movements. Your mind will be distracted and foggy.
You just won't perform at your peak.
You will burn lots of Calories when Skiing, when it's colder, when it's warmer, all the time... so getting your nutrition intake spot on is key to success.
Proteins, Carbs, Electrolytes, Vitamins and Minerals.
Set yourself up with a good breakfast.
Start with a pint of water with freshly squeeed lemon juice added, then take some fresh fruit. Then enjoy some porridge and a banana with nuts and seeds. Then enjoy some organic eggs. Some fresh breads. Top it off with a glass of real freshly squeezed orange juice (no supermarket pre bottled junk) and finally a hot cup of green tea.
On the ski slopes take plenty of energy, a banana, nuts, dried fruit, an apple, maybe a bit of dark chocolate. Ensure you stay correctly hydrated with as much natural food.
Lunch could consist of fresh fruit first, hot soup and salad if you don't want to over eat, or maybe a good plate of Spaghetti and a generous mixed salad.
Breakfast - Porridge / Banana. Egg on the side.
Keep hydrated + keep your salts topped up.
Have a large salad and soup for lunch.
Stop for a hot drink - Live a little.
Carry some dried fruit / Nuts, Dates.