Altitude anorexia, the invisible enemy of mountain pass climbers and trail runners
You're at the top of a 2600m pass, you know you need to eat, and yet… nothing. No appetite at all. This is a phenomenon well known to Tour de France cyclists on the great Alpine climbs and to trail runners operating above 2500-3000m: appetite evaporates just as energy needs explode. This paradox has a scientific name: altitude anorexia.
This is exactly the kind of situation where a standard fueling plan stops being enough. The Ograal long-distance fueling module, designed for efforts over 5 hours, integrates adaptation to extreme conditions — heat, altitude, elevation gain — to automatically adjust the texture and timing of intake when your natural appetite lets you down.
Definition: altitude anorexia refers to the suppression of hunger sensation induced by altitude hypoxia, starting around 1500-2000m, via a drop in ghrelin (the hunger hormone) and changes in other appetite-regulating hormones such as leptin and CCK.
The problem is that this appetite drop occurs exactly when the body needs more energy: daily energy expenditure increases by 15 to 20% at altitude, due to increased respiratory work, cold exposure, and the extra effort of moving through hypoxic terrain.
What happens in the body from 1500m altitude onwards?
The mechanism behind altitude anorexia is now well documented. As early as the 1990s, researcher Bengt Kayser demonstrated the links between altitude exposure and weight loss driven by a spontaneous reduction in food intake, well before any depletion of energy reserves (Kayser, 1994, PubMed). More recent work has clarified the hormonal mechanism: hypoxia suppresses secretion of acylated ghrelin, the hormone that normally stimulates hunger, while satiety hormones like leptin and cholecystokinin (CCK) remain elevated (simulated altitude study at 4,000m, Journal of Applied Physiology).
The concrete result on the ground: runners and cyclists at altitude spontaneously reduce their food intake by 30 to 40%, while their actual caloric needs increase at the same time. This gap between intake and needs, repeated over several stage days or a skyrunning race, can create a severe energy deficit that degrades performance and recovery.
A reference paper by Braun and Mawson further detailed the specific nutritional requirements at high altitude, emphasizing the need to increase protein intake and preserve lean mass despite reduced appetite (Braun & Mawson, 1999/2001, PubMed).
Tour de France 2026: 5,450m of elevation gain on the penultimate Alpine stage
The 2026 Tour de France, starting in Barcelona on July 4, features a particularly demanding Alpine profile at the end of the race, with the crossing of the Col du Galibier (2619m) and a finish at Alpe d'Huez. Stage 20, the penultimate mountain stage, packs around 5,450m of elevation gain on its own — a profile that places many riders above the 2000m threshold for several consecutive hours, precisely the zone where altitude anorexia sets in.
For riders in the peloton as well as amateur cyclosportive riders dreaming of climbing these same passes, the difficulty isn't just physical: it's also forcing food intake when the hunger signal has disappeared. It's as much a mental challenge as a nutritional one.
How Tove Alexandersson fuels her skyrunning outings above 3000m
Tove Alexandersson, the Swedish athlete and multiple world champion across six different disciplines (orienteering, ski orienteering, skyrunning, ski mountaineering, trail running, SkySnow), holds the world n°1 spot in the ITRA ranking in 2026 and joined the Salomon international team in March 2026 to focus more on trail running. In May 2026, she shattered the Zegama-Aizkorri Marathon record in 4:08:09, a race that regularly climbs above 1500-2000m altitude.
Skyrunning, her discipline of choice, most often takes place between 2500 and 4000m — a zone where altitude anorexia is essentially guaranteed. Athletes at this level structure their nutrition in advance: they favor split, frequent intake tested in training under similar conditions, rather than hoping appetite will return naturally during the race.
Key takeaways
- From 1500-2000m onwards, ghrelin (the hunger hormone) drops under hypoxia's effect: appetite decreases by 30 to 40%.
- At the same time, daily energy expenditure increases by 15 to 20% at altitude.
- Stage 20 of the 2026 Tour de France packs around 5,450m of elevation gain, with the Col du Galibier (2619m) and Alpe d'Huez.
- The field rule: eat before you're hungry, every 20-25 minutes at altitude versus 30-45 minutes at sea level.
Concrete strategies to counter altitude anorexia
Facing an appetite that disappears just as needs explode, several practical levers help limit the damage:
- Favor liquid forms: liquid gels, maltodextrin-based drinks, concentrated soups. Liquids go down more easily than solids when appetite is suppressed and digestion is slowed by hypoxia.
- Choose ultra energy-dense foods: almond butter, dates, compact white rice, dried fruit and nuts. These foods deliver maximum calories for minimum volume to swallow.
- Shift your intake timing: eat before you're hungry, in small amounts every 20 to 25 minutes at altitude, versus 30 to 45 minutes at sea level, to avoid waiting for a hunger signal that won't come.
- Plan ahead with a written strategy: at high altitude, decision-making is also affected by mild hypoxia. A fueling plan set in advance, without improvisation, limits missed intake windows.
Comparison table: fueling at sea level vs. at altitude
This type of adjustment is exactly what we cover in our article on trail nutrition in hot conditions, where the same logic of adapting to extreme conditions applies as much to altitude as to heatwaves: in both cases, you need to step out of autopilot and consciously adjust your plan.
For long outings at altitude, a well-tolerated gel remains a safe bet — a HYDROGEL orange energy gel 67ml offers a more fluid texture, making it easier to swallow when appetite is at its lowest.
UTMB Chamonix: the other race where altitude dictates fueling
In late August 2026, the UTMB in Chamonix will confront runners with altitude sections around the Grand Col Ferret and Col des Fours, above 2500m, on a course that exceeds 24 hours of effort for the majority of the field. On this type of ultra-long event, altitude anorexia stacks on top of the classic gut fatigue experienced by ultra-trail runners, which makes nutritional planning all the more critical. Experienced runners know they'll need to force food intake through the altitude sections, even without feeling hungry, or risk blowing up further down in the valley.
FAQ
At what altitude does altitude anorexia start?
The first effects are documented from around 1500-2000m, with increasing intensity above 2500-3000m, where hypoxia becomes more pronounced and ghrelin suppression more marked.
Why do I lose my appetite in the mountains during a big effort?
Altitude hypoxia suppresses ghrelin secretion, the hunger hormone, while keeping satiety hormones like leptin elevated. Your body stops sending the signal, even though your needs have increased.
What should I eat when appetite disappears at altitude?
Favor liquid and semi-liquid forms (gels, maltodextrin drinks) and ultra energy-dense foods like almond butter or dates, in small amounts every 20-25 minutes.
Does altitude anorexia affect all athletes the same way?
No, sensitivity varies with individual acclimatization, ascent speed, and altitude experience. Seasoned athletes like Tove Alexandersson structure their nutrition in advance rather than relying on appetite.
Sources
- Kayser B. (1994), "Nutrition and high altitude exposure", European Journal of Applied Physiology — PubMed
- Snyder E.M. et al., "Influence of rest and exercise at a simulated altitude of 4,000 m on appetite, energy intake, and plasma concentrations of acylated ghrelin and peptide YY", Journal of Applied Physiology — DOI: 10.1152/japplphysiol.00090.2011
- Braun B. & Mawson J.T. (1999), "Nutrient requirements at high altitude" — PubMed
- Tour de France 2026: official route, Grand Départ Barcelona (July 4), Col du Galibier (2619m), Alpe d'Huez, stage 20 — letour.fr
