Last summer, I bailed 2 pitches below the summit of the 5,600m NE Buttress of Slesse Mountain in the Bugaboos, convinced I was too out of shape to finish the route. Three days into the trip, my hands were shaking so bad I couldn't clip a quickdraw, my head was throbbing, and I could barely summon the energy to pull on my climbing shoes. I'd packed nothing but store-bought energy gels, spicy beef jerky, and a bag of trail mix full of chocolate that had melted into a solid brick by day two. It wasn't until I sat in base camp with a local alpine guide who'd spent 20 years guiding in the range that I realized my mistake: I'd treated high-altitude expedition nutrition like a day trip to the crag, when the demands of long days at elevation are almost nothing like single-pitch sends.
High-altitude climbing throws a wrench in every standard nutrition rule you've learned for gym sessions or local crag days. At 3,000m and above, your body burns 30-50% more calories per day than it does at sea level, even when you're sitting still, thanks to the extra work your heart and lungs have to do to oxygenate tissues and acclimate to thin air. Appetite suppression is universal at elevation, driven by elevated cortisol levels and reduced blood flow to your stomach, so most climbers eat 20-30% less than they need, even when they're actively trying to fuel up. Taste buds go dull, so salty, bitter, or heavily processed foods taste off, and freezing temperatures turn soft, high-fat foods into inedible rocks by midday. If you're not tailoring your food to these factors, you're setting yourself up to bonk, develop altitude sickness, or bail on a route you've spent months training for.
The best nutritional plans for high-altitude expeditions aren't one-size-fits-all: they shift to match the three distinct phases of your trip, each with different calorie and macro needs. I've tested this structure on 6 alpine expeditions over the past 3 years, and it's cut my bonk rate by 100%---no more early bailouts from low blood sugar or altitude headaches tied to poor fueling.
Approach & Hiking Days
The goal of these 4-8 hour days hauling 30+ lbs of gear to base camp is steady, consistent energy with zero GI distress, no matter how steep the scree slope. Aim for a 55% carbs, 25% protein, 20% fat macro split to keep your energy stable without weighing you down. Skip high-fiber foods here: the combination of altitude and heavy exertion can cause major GI bloat, which is the last thing you want when you're already struggling under a heavy pack. Stick to easy-to-digest, calorie-dense options:
- Pre-hike breakfast: Instant oatmeal mixed with peanut butter powder, dried blueberries, and a pinch of salt, plus a pre-peeled hard-boiled egg you packed the night before.
- On-the-move snacks every 45 minutes: Dried mango slices, salted pretzels, a small handful of roasted edamame, or a no-added-sugar granola bar that won't melt in the heat of your pack.
- Trail lunch: A tortilla wrap stuffed with hummus, sliced turkey, spinach, and a sprinkle of cheese, wrapped in foil so it stays pliable even in cold temps.
- Camp dinner: Dehydrated lentil and rice curry mixed with a scoop of whey protein, plus a handful of dried apricots for extra fast-acting carbs.
Base Camp Rest Days
These low-exertion days, spent acclimating, resting, or doing short approach hikes, are all about recovery and building glycogen stores for your summit push. Bump your protein intake slightly to a 30% share of your macros to repair muscle damage from the approach, and keep carbs at 50% to top up your energy reserves. Meals here can be a little more indulgent, since you're not hauling them up a mountain:
- Breakfast: Shelf-stable chia pudding mixed with whole milk powder and banana chips, or scrambled eggs if your camp stove is working well.
- Lunch: Tuna packets mixed with mayo and crackers, or a block of hard aged cheese paired with a crisp apple.
- Snacks: Shelf-stable Greek yogurt, 70%+ dark chocolate (lower sugar means no mid-afternoon crash), and low-sodium beef jerky.
- Dinner: Hearty dehydrated chili with beans, topped with a dollop of shelf-stable sour cream and shredded cheddar. Drink 3-4 liters of water a day here, mixed with an electrolyte tablet: altitude dehydrates you faster than you realize, even if you don't feel sweaty, and mild dehydration is the #1 cause of altitude headache.
Summit Push & Route Pitch Days
This is the most critical phase, where a bonk can put you in real danger. These 8-12 hour days of high-intensity exertion in freezing temps call for a 60% carbs, 20% protein, 15% fat split: carbs are the easiest fuel for your body to access when you're working hard at altitude, and they take far less energy to digest than fat or protein. All food here needs to be bite-sized, no-prep, freeze-proof, and easy to eat with gloves on---no fumbling with wrappers or thawing frozen food mid-pitch:
- Pre-push breakfast: A bagel slathered with peanut butter and a drizzle of honey, plus a banana wrapped in a wool sock to keep it from freezing.
- On-the-move snacks every 30 minutes: Chewy carb blocks, fig newtons, dried pineapple, or a small squeeze pouch of unsweetened applesauce.
- Belay rest snacks: Small blocks of cheddar cheese, single-serve almond butter pouches, or pre-cut peanut butter and jelly sandwiches wrapped in wax paper so they don't freeze solid. Keep a small stash of emergency high-calorie food in your jacket pocket at all times: a travel-size jar of Nutella, cookie butter bites, or a pack of peanut butter M&Ms. If you start feeling lightheaded or shaky mid-pitch, a few spoonfuls will bring your blood sugar back up in 2 minutes flat, no stopping required.
The biggest mistake I see climbers make on expeditions is cutting calories to avoid gaining weight, or relying solely on sugary energy gels for the entire summit push. Gels are great for a 15-minute boost, but if you're only eating sugar all day, you'll crash hard halfway up your route. Pair every sugary snack with a small amount of fat or protein---like a handful of almonds with your energy gel---to keep your blood sugar stable for hours at a time. And never skip electrolytes: altitude makes you urinate far more than you do at sea level, even if you don't feel sweaty, so mild dehydration will feel exactly like altitude sickness, with headaches, nausea, and fatigue that won't go away no matter how much you acclimatize.
I used this exact nutrition plan on my second attempt at Slesse two months after my bail, and I finished the route without a single bonk, even when we got caught in a late afternoon snowstorm on the descent. I didn't feel shaky, I didn't get a pounding headache, and I had enough energy to help haul the haul bag the last 2 miles back to the car. It's easy to obsess over training plans, gear, and route beta when you're preparing for an alpine expedition, but the difference between sending your goal route and bailing halfway up often comes down to what's in your pack, not just what's on your harness.
Have a high-altitude nutrition hack that saved your trip? Drop it in the comments below.