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Antarctica Solo Crossing Food: The Calorie Equation

By James Frost, Founder of Flaming Phoenix. Phoenix Bars have been used on Arctic and polar expeditions, Marathon des Sables, Aconcagua, and ocean rows. They've been carried to the summit of Everest.

Last updated: May 2026

The short answer

An unsupported Antarctic crossing is the hardest endurance nutrition problem on earth. You'll burn 7,000 to 10,000 calories per day for 60 to 110 days, in temperatures down to minus 50°C, on a polar plateau at 3,000 to 3,500m of altitude, dragging a 100 to 230kg pulk that contains every calorie you'll consume. There is no resupply. There is no rescue. The calorie maths either closes or it doesn't.

Modern crossings target 5,500 to 7,000 calories per day intake. Even at this rate, all known crossings have ended in significant weight loss. The food plan has to thread the needle between three competing constraints: enough calories to survive, light enough to drag, and varied enough to actually eat for three months.

This guide synthesises what we've learned from a century of Antarctic crossings, breaks down the calorie equation, and gives you a practical provisioning framework for a 60 to 110 day attempt.

The calorie equation

Antarctic crossings are governed by an equation that has no perfect solution.

The more food you carry, the heavier your pulk. The heavier your pulk, the more calories you burn dragging it. The more calories you burn, the more food you need. Somewhere there's a theoretical optimum where adding or removing one more energy bar changes your maximum range. The unanswered question for decades was whether that optimum range exceeded the width of Antarctica.

We now know it does, but barely. Colin O'Brady proved it in 2018 with a 54-day, 932-mile solo unsupported crossing, hauling a sled that started at 375 pounds. Henry Worsley died trying the same thing in 2016, 900 miles in. The margin between success and failure is calories per gram of pack weight.

The practical implication: every food choice is a maths problem. A food at 4 calories per gram is heavier-per-calorie than a food at 5 cal/g. Over 90 days, that 25% density difference compounds into 10kg+ of pulk weight, which is the difference between finishing and not.

What we've learned from a century of Antarctic crossings

The history of polar nutrition is a history of getting the calorie equation wrong, then less wrong.

Scott (1911 to 1912): 4,200 to 4,600 cal/day. Catastrophically insufficient. The fatal flaw was not just bad luck or weather; it was that Scott's party was eating roughly half of what their bodies were burning. Modern analysis suggests they were burning 6,000+ cal/day. They starved before they froze.

Stroud and Fiennes (1992 to 1993): 1,600 miles, 96 days, two-person unsupported. The first crossing where energy expenditure was measured scientifically using isotope-labeled water. The result was a shock: 7,000 cal/day burn average, with a 10-day stretch above 11,000 cal/day on the polar plateau ascent. They ate 5,000 cal/day. Stroud lost 48 pounds. Fiennes lost 54 pounds. Both finished, just.

Worsley (2015 to 2016): solo unsupported attempt. Died 30 miles from completion of an 1,100-mile crossing, after 71 days. Multi-organ failure, dehydration, and exhaustion. The expedition demonstrated that even with modern nutrition, the calorie deficit can become structurally dangerous before the finish line.

O'Brady (2018): 932 miles, 54 days, solo unsupported. First successful crossing of the Antarctic landmass solo and unsupported. His provisioning was based on roughly 7,000 cal/day at 5,000 cal/lb of food (a target density), with a custom-formulated bar from the Standard Process Nutrition Innovation Center. The fast pace meant the calorie deficit was front-loaded into a shorter window.

Andrews and Stephenson (2023): 75-day attempted full crossing. Reached the South Pole but a short Antarctic summer forced an early finish. Provisioned by clinical dietician Andrea Hordern Andrews at 6,500 to 7,000 cal/day, with 1.2 to 1.3kg of food per person per day, totalling 90 to 100kg of food per person. Daytime rations split into accessible savoury bags (cheese, jerky, pork sticks) and sweet snack bags (chocolate, protein bars, nut butters), plus high-calorie nutritionally complete drinks at first break.

O'Brady (2025): 110-day, 1,780-mile attempt in progress. Sled weight roughly 500 pounds, 400 of which is food and fuel, targeting 10,000 cal/day burn. Largest food carry in modern unsupported polar history.

The pattern across all of these: the calorie target has risen as our measurement has improved. Modern crossings provision at 6,500 to 7,000 cal/day intake, and the science suggests even this is below true burn rate.

What the science says about polar calorie demand

Two studies are the foundation of modern polar nutrition planning.

Stroud and Fiennes 1993 metabolic study (1,600-mile Antarctic traverse): average 7,000 cal/day burn, with 11,000 cal/day on plateau ascent days. Demonstrated that the cold and exertion of polar travel together drive basal metabolic rate up by 30 to 50% above sea-level baseline.

93-day solo Antarctic crossing case study (published 2021): showed that intake of 5,058 to 5,931 cal/day allowed recovery of leptin and nutritional status between phases of extreme physical and psychological hardship. Below this range, the explorer's albumin levels dropped and recovery between hard phases became incomplete.

SPEAR-17 (2017, six British Army Reservists, 67-day Antarctic crossing): measured weight loss of 7% body mass even with 6,500 cal/day intake, with 53% reduction in fat tissue. Confirmed that thermoregulatory demands on Antarctica add a significant calorie tax beyond exertion alone.

The synthesis: aim for 6,500 to 7,000 cal/day intake minimum on a 60+ day Antarctic crossing. Accept that you will likely lose 5 to 10kg over the duration regardless. The goal is to keep the deficit within a survivable range, not to eliminate it.

For more on calorie density principles that apply across all expeditions, see Calorie-Dense Foods.

The fat vs carb debate at minus 50°C

Antarctic nutrition has been the front line of the fat-vs-carb debate in endurance science for over a century.

The traditional argument for fat: 9 cal/gram vs carb's 4 cal/gram, so fat is the only way to hit 6,500+ cal/day intake without absurd pulk weight. Amundsen's 1911 South Pole party ate roughly 60% of calories from fat. Modern advocates of high-fat polar diets cite this same logic.

The modern argument for carbs: at sustained polar workloads, carb metabolism delivers steadier daily power output and faster overnight recovery. Carbs require less oxygen to metabolise, which matters at the 3,000 to 3,500m polar plateau altitude. The SPEAR-17 study and the 2021 solo crossing case study both showed performance advantages for higher-carb provisioning even when total calories were matched.

The current consensus from polar dietitians sits at roughly 50 to 55% carbs, 30 to 35% fat, 15 to 20% protein. Compare to Aconcagua's 65% carb target (an altitude problem) and traditional polar's 50%+ fat (a weight-and-warmth problem). Antarctica's modern macro split sits in the middle, slightly carb-favoured.

Phoenix Bars deliver 66g of carbohydrate per 120g bar (47% of calories from carbs), which fits the modern polar carb-favoured macro target. The remaining calories are a fat-and-protein mix that contributes to thermoregulation and satiety. For more on the solid-food-vs-gel decision in cold conditions, see Energy Gel Alternatives and Ultra High Carb Solid Foods.

What survives at minus 50°C

The cold-stability problem is more severe on Antarctica than anywhere else on earth. The polar plateau hits minus 50°C in the interior; coastal sections see minus 30°C with wind chill into the minus 60s. Almost nothing you can buy in a supermarket survives this.

Stays edible at minus 50°C, accessible from a chest food bag: Phoenix Bars (formulated to stay soft), butter and oils kept inside body layers, hard cheese (brittle but chewable in pieces), salami and dried sausage, glucose tablets, boiled sweets, peanut butter (slow), Stroopwafels (just), powdered drinks.

Edible only after thawing in the tent: chocolate (fractures like glass cold), nuts (frostbite-cold against teeth), dried fruit (ice rocks), most conventional energy bars (rock-hard frozen), tortillas, crackers, jerky.

Unusable on the ice: anything water-based or fresh, bread, gels (freeze solid in pulks within hours, the squeeze format is unworkable in polar gloves anyway), pre-mixed drinks, ready-to-eat meals, rehydrated foods.

The chest food bag rule: every successful modern Antarctic skier carries a fabric food bag on their chest, under their wind shell, against the body. It holds the day's snacks. Body heat keeps them at jacket temperature (warmer than ambient by 30 to 40°C). Anything not in the chest bag freezes solid within hours and becomes useless until tent time.

The three windows: daily food rhythm on the ice

The eating pattern that works on Antarctic crossings has three distinct windows, each with different requirements and constraints.

Tent breakfast (45 to 60 minutes, 1,500 to 2,000 calories). Stove already lit melting water. Polar standard is high-calorie porridge: oats, powdered milk, butter, sugar, plus a Phoenix Bar broken in for an extra 557 calories of carb-led density and texture variety. Hot drink, sometimes a second hot drink. Goal is to over-eat at breakfast because lunch is essentially impossible. See High Calorie Porridge for the porridge mechanics.

On the move (8 to 10 hours, 3,000 to 4,000 calories). No proper meal stops, just 5-minute breaks every 75 to 90 minutes. Eat from the chest food bag during breaks. Standard polar pattern is alternating savoury (cheese, salami, jerky) and sweet (Phoenix Bars, chocolate, Stroopwafels) at each break to manage flavour fatigue across 60+ days. Phoenix Bars work in this window because the soft texture stays edible chest-pocketed and 557 calories per bar covers the calorie target for one break-and-ski cycle.

Tent dinner (60 to 90 minutes, 2,000 to 3,000 calories). Fuel-efficient hot meal. Most expeditions use freeze-dried mains (Real Turmat, Firepot, Mountain House) bumped up with extra butter, oil, dehydrated vegetables, and powdered milk. The pattern is to stuff yourself in the evening so you sleep warm and full, then ration on-the-move calories the next day. Hot drink, usually two.

For the broader principles of self-supported expedition fuelling, see the Ultra-Endurance and Expedition Nutrition Guide.

Provisioning maths for a 60 to 90 day Antarctic crossing

The breakdown for a typical solo unsupported attempt of 60 to 90 days on the South Pole or full continental routes.

Total food weight: 1.2 to 1.4kg per person per day, depending on macro split and density. For 75 days at 1.3kg, that's 97.5kg of food alone, before fuel, gear, or sled weight. This is consistent with the Andrews and Stephenson 2023 provisioning of 90 to 100kg per person.

Calorie density target: 5 to 6 calories per gram across the full food bag. Below 5 cal/g, the maths doesn't close. Above 6 cal/g requires near-pure-fat foods, which are hard to eat in volume.

Daily food bag composition:

Breakfast: 250g of porridge ingredients (oats, milk powder, butter, sugar) plus 1 Phoenix Bar = 1,500 to 2,000 cal
On-the-move: 400 to 500g of mixed snacks (2 to 3 Phoenix Bars, cheese, salami, chocolate, Stroopwafels) = 2,500 to 3,500 cal
Dinner: 200g of freeze-dried main plus 50g of butter or oil add-in = 1,500 to 2,500 cal
Hot drinks and treats: 100g of powdered drinks, sweets, treats = 400 to 600 cal

Total daily Phoenix Bar count: 3 to 4 bars per day across breakfast and trail snacks.

Total Phoenix Bar provisioning for a 75-day crossing: 225 to 300 bars per skier. This typically packs as nine 30-bar Complete Bundles (270 bars) plus one Starter Bundle (12 bars) for emergency reserve, or equivalent.

Order value at standard pricing: roughly £1,125 to £1,500 per skier on Phoenix Bars alone. For polar expedition orders above 100 bars, contact me directly for expedition pricing rather than ordering through standard bundles. We've supported expedition orders of 200+ bars before and can ship internationally to Punta Arenas, Cape Town, or Hobart for pre-staging.

How Phoenix Bars work on an Antarctic crossing

Phoenix Bars solve five of the six fundamental Antarctic food problems simultaneously, which is why they fit naturally into modern polar provisioning despite being a UK product without polar marketing.

Cold-stability: stays edible at minus 50°C inside a chest food bag. Most conventional bars freeze solid within hours of leaving the tent.

Calorie density: 4.6 cal/gram, comfortably above the 4 cal/g floor that disqualifies most foods from polar use, sitting just below the 5 to 6 cal/g target by relying on additional fat sources (butter, oil) elsewhere in the food plan.

Carb load: 66g of carbohydrate per bar aligns with the modern carb-favoured polar macro split (50 to 55% carbs).

Variety across 75+ days: six flavours rotate the palate over a 90-day window. Salted Caramel and Ginger sit at the savoury end and reset taste fatigue when sweet bars stop working around day 20 to 25. Variety isn't a luxury on a 75-day crossing; it's a primary success factor.

Hot meal capability: a Phoenix Bar plus boiling water becomes a 557-calorie porridge in 2 minutes, doubling the bar's utility because the same product works as a chest-bag trail snack and as a breakfast component.

Shelf life: two-year shelf life supports the typical 4 to 8 month polar planning horizon. Most Antarctic provisioning is shipped to Punta Arenas (the standard staging port) months in advance.

What they don't replace: stove-cooked dinners (you still need freeze-dried mains for variety and calorie volume), butter and oil (the fat density that makes the maths close), the specialty high-calorie liquid drinks some expeditions use at first break, and the savoury element (cheese, salami) that resets taste fatigue.

For practical guidance on the porridge format, breaking-into-pieces method, and chest-bag access patterns, see How To Use Phoenix Bars.

How Antarctica differs from Greenland

For skiers who've done Greenland and are considering Antarctica, the differences matter for food planning.

Duration: Greenland is 25 to 34 days. Antarctica is 60 to 110 days. The time horizon multiplies the variety problem and the cumulative calorie deficit.

Cold: Greenland's interior hits minus 25 to minus 42°C. Antarctica's polar plateau hits minus 50°C. The food cold-stability filter is harsher. More foods that survive Greenland fail on Antarctica.

Altitude: Greenland's high point is 2,500m. Antarctica's polar plateau is 3,000 to 3,500m. The altitude adds appetite suppression and slowed digestion to the already heavy load of cold-stress eating.

Pulk weight: Greenland starts at 80 to 100kg. Antarctica starts at 100 to 230kg depending on duration and route. Calorie burn from hauling is correspondingly higher.

Remoteness: Greenland has rescue options. Antarctica essentially does not, mid-traverse. Food failure has a higher consequence.

If you've done a Greenland crossing and are planning Antarctica, your food plan needs to scale up calorie density, scale up variety, and scale up reserve. See Greenland Crossing Food for the comparable framework on the shorter expedition.

Frequently asked questions

How many calories do I need per day on an Antarctic crossing? Modern science suggests 6,500 to 7,000 calories per day intake minimum. True burn is higher (7,000 to 10,000 cal/day) but the calorie equation makes it impossible to fully match burn. Expect 5 to 10kg of weight loss over a 60+ day crossing regardless of how well you provision.

What's the calorie density floor for Antarctic food? 5 calories per gram across the full food bag. Below this, the pulk becomes too heavy to drag the full distance. Hitting 5 cal/g requires careful selection: butter, oils, calorie-dense bars, freeze-dried mains, hard cheeses, and processed fats. Most fresh and minimally-processed foods don't make the cut.

What's the difference between an Arctic and Antarctic crossing food plan? Antarctica is colder (minus 50°C vs Arctic's minus 40°C), longer (60 to 110 days vs Arctic's 25 to 60 days), higher altitude (polar plateau is 3,000 to 3,500m), and has higher pulk weights. The food plan needs higher calorie density, more variety, more cold-stability, and a larger emergency reserve.

Will Phoenix Bars stay edible at minus 50°C? Yes, when carried in a chest food bag against the body where the temperature is held at jacket-internal warmth (typically 30 to 40°C above ambient). Even at ambient minus 50°C, body-warm bars stay soft. This is the standard polar carry pattern.

How many Phoenix Bars do I need for a 75-day Antarctic crossing? Roughly 225 to 300 bars per skier, depending on macro split and how heavily you rely on bars vs other carb sources. A typical breakdown is 1 bar per day for breakfast porridge plus 2 to 3 bars per day for trail snacks plus 10 to 15 bars in emergency reserve. Most polar skiers order through expedition pricing for volumes above 100 bars.

Should I do high-fat or high-carb on Antarctica? The current consensus is 50 to 55% carbs, 30 to 35% fat, 15 to 20% protein. Modern science favours carb-led provisioning over the traditional fat-heavy polar diet for daily power output and overnight recovery. Fat still matters for thermoregulation and calorie density, but it shouldn't dominate.

What about gels for the polar plateau? Gels freeze solid in pulks within hours and the squeeze format is unworkable in polar gloves at sub-zero. Solid bars and chews work; gels don't. Almost no successful modern Antarctic crossing has relied on gels. Full breakdown at Energy Gel Alternatives.

How do I provision food for an Antarctic crossing logistically? Most provisioning ships to the staging port (Punta Arenas for ALCI, Union Glacier; Cape Town for some private operators; Hobart for Australian routes) two to four months in advance. Phoenix Bars' two-year shelf life supports this timeline. Bulk expedition orders ship internationally with proper customs documentation.

How does Antarctica compare to Greenland for food planning? Antarctica is 2 to 3 times longer, 5 to 10°C colder, higher altitude, and heavier pulk. Every food planning constraint is more severe. If you've done Greenland, scale up calorie density, variety, and reserve before attempting Antarctica. See Greenland Crossing Food for the lower-difficulty framework.