Training above 2,000 metres rewrites your nutritional demands in ways most athletes never account for.
Training above 2,000 metres rewrites your nutritional demands in ways most athletes never account for.
Spend a week above 2,500 metres and your appetite often disappears precisely when your body needs fuel most. It is one of altitude's more disorienting contradictions, the physiological demand goes up while the hunger signal goes quiet.
This is not a minor inconvenience. At elevation, the body is running a different kind of programme. Red blood cell production accelerates in response to reduced oxygen availability. Ventilation rate increases. The kidneys work harder to regulate fluid balance. Each of these processes has a nutritional cost, and most athletes arrive at altitude without adjusting for any of them.
The stimulus for altitude adaptation, the whole point of going up, is erythropoiesis, the production of new red blood cells. That process is iron-dependent. Without adequate iron stores, the body cannot build the haemoglobin needed to carry more oxygen, and the training block becomes physiologically pointless regardless of how hard the sessions are.
Athletes who arrive at altitude with borderline ferritin levels will not adapt well. The threshold matters: most sports medicine practitioners working with endurance athletes look for ferritin above 30 micrograms per litre before altitude exposure, with higher being better. Red meat, organ meat, shellfish, and fortified cereals all contribute. Pairing iron-rich foods with vitamin C improves absorption; pairing them with calcium or tannins from tea and coffee reduces it. These details are worth knowing before the camp begins, not during it.
Altitude increases the relative contribution of carbohydrate to energy expenditure. The body leans more heavily on glycolytic pathways when oxygen is limited, which means carbohydrate stores deplete faster at the same perceived effort. At the same time, appetite suppression, driven partly by elevated leptin and altered ghrelin signalling at altitude, makes it harder to eat enough.
The practical result is that athletes in altitude camps frequently under-fuel without realising it. They feel less hungry, eat less, and then wonder why sessions feel disproportionately hard by day four or five. Structured eating, meals and snacks at fixed intervals regardless of hunger, is not a rigid habit to be broken at altitude; it is a functional response to a known physiological distortion.
Increased breathing rate at altitude means more water lost through respiration. Urine output also tends to increase in the first few days as the kidneys adjust bicarbonate excretion to manage the respiratory alkalosis that comes with hyperventilation. The net effect is a higher daily fluid requirement that many athletes do not account for.
Electrolyte balance matters here too. Sodium losses through sweat remain significant even in cooler mountain environments, and the combination of increased fluid loss and reduced appetite can create a deficit that compounds fatigue and impairs recovery between sessions.
Altitude training is a deliberate physiological stressor. The adaptation it produces, more red blood cells, improved oxygen-carrying capacity, enhanced buffering, is the goal. But those adaptations require raw materials, and the environment that drives them simultaneously suppresses the appetite signals that would normally prompt athletes to supply them.
Arriving at altitude with iron stores already optimised, a plan to eat structured carbohydrate regardless of hunger, and a clear awareness of elevated fluid requirements is not overcomplicating the process. It is recognising that the body's normal feedback mechanisms are temporarily unreliable, and choosing to override them with something more deliberate.
The altitude does the work. Nutrition determines whether the body can respond to it.