Nutrition is critical for optimal performance in sports, especially resistance sports. The organism oxidizes fats and carbohydrates normally up to 5,000 metres, and weight loss below this altitude can be attributed to inadequate calorie intake. The diet of climbers should be rich in carbohydrates and balanced in the remaining nutrients; their traditional fat-rich diets can lead to chronic muscle fatigue. A descriptive cross-sectional study was performed on the diet of a group of high-mountain climbers at their base camp (4,500 m). Given that their aim was to replenish energy deposits, the mean intake of 11.85 MJ/day (2,833 kcal/day) provided an inadequate supply of energy and micronutrients. A carbohydrate-rich diet favours acclimatization and the capacity for recovery, therefore their 39.5% carbohydrate intake was very low. Their daily intake of 1.5-2.5 g/protein/kg of bodyweight was very similar to recommendations (1.5- 2.0 g/kg/day). The climbers underwent a drastic change from their habitual Mediterranean diet, rich in monounsaturated fats (largely olive oil), to a diet rich in polyunsaturated fats (largely soy oil). The Sherpa-prepared diet on this expedition was not balanced. It was rich in saturated polyunsaturated fats and relatively poor in proteins and especially carbohydrates, similar to the traditional diet of climbers. This diet does not favour acclimatization because metabolism of excessive fats requires increased oxygen at the expense of other tissues.