Traveling to your favorite ski destination often strains your wallet-and your lungs-but few people realize the stress it puts on your stomach. Adjusting your diet to higher altitude will help keep energy levels up and can also help fend off altitude sickness. Water is the first step to winning this battle, because breathing at altitude expends more moisture than breathing at sea level. Also, because your metabolic rate speeds up to increase your oxygen intake, you need more fuel to maintain the faster pace. Atkins followers beware: Carbohydrates are the key to sustaining your energy levels at elevation, because you burn carbs instead of fats in order to dissolve more oxygen into the bloodstream.