It's really simple to lose weight even if you are skiing. You just need to eat proteins every meal, veggies are really important also because most of them have the right amount of nutrients that you need for skiing. Switch from white rice and white pasta to brown rice and whole wheat pasta (White rice+pasta are basically sugar and there's not enough fibers in them which mean you will be full for 2 hours then you will feel really hungry after that, compare to whole wheat pasta that keep you full longer.) eat carbs for breakfast (whole wheat or grains bread) and lunch but avoid it for dinner. Cut sweet products (such as candies, cookies, etc) and eat more fruits instead. Have a cheat meal once in a week to boost your metabolism, drink water (8 glasses a day) and you should be in shape in few months and this is not going to affect your body : you won't be tired at all and you should also improve your skiing !