Do you need to eat more at higher altitude? The surprising nutritional truth

January 13, 2026 •

4 min read

A study on simulated Everest ascents found climbers had a significant involuntary weight loss of up to 5 kg, despite ample food. So, do you need to eat more at higher altitude? The answer is nuanced, involving altered metabolism, reduced appetite, and increased energy expenditure.

Quick Summary

The body's energy needs and metabolism change significantly at higher altitudes due to hypoxia. Reduced appetite and increased caloric expenditure mean many people eat less despite needing more calories. Strategic nutrition and hydration are vital to combat weight loss and prevent altitude sickness. Prioritizing carbohydrates, lean protein, and staying well-hydrated is crucial for successful acclimatization and sustained energy.

Key Points

Eat More Calories: Despite suppressed appetite at altitude, your body's metabolic rate increases, so you need to consume more energy to avoid unhealthy weight loss.
Prioritize Carbohydrates: Your body is more efficient at using carbohydrates for fuel in low-oxygen environments, so increase your intake of complex carbs like whole grains and dried fruits.
Stay Hydrated: The dry air and increased urination at altitude accelerate dehydration, so drink 3-4 liters of water or electrolyte-enhanced fluid daily, regardless of thirst.
Eat Small, Frequent Meals: Opt for several smaller, more frequent meals throughout the day instead of large ones. This is easier on a stressed digestive system and maintains steady energy levels.
Avoid Heavy, Fatty Foods: Fatty and processed foods are harder to digest, which can lead to gastrointestinal discomfort at altitude. Stick to lighter, nutrient-dense options.
Acknowledge Reduced Appetite: Be aware that your appetite will likely decrease. Make a conscious effort to eat and drink consistently, and bring a variety of palatable, appealing snacks.

Your body's metabolic shift at high altitude

When you travel to a higher elevation, the reduced oxygen pressure (hypoxia) forces your body to undergo several physiological changes to adapt. The air is thinner, meaning each breath provides less oxygen. This triggers an increase in your basal metabolic rate (BMR)—the energy your body uses at rest—as your heart rate and breathing intensify to compensate. Your body also shifts its primary fuel source towards carbohydrates, which require less oxygen to metabolize than fats. While this is an efficient adaptation, it depletes your limited glycogen stores more rapidly.

The paradoxical effect of altitude on appetite

One of the most challenging aspects of high-altitude nutrition is the suppression of appetite, often referred to as 'mountain anorexia'. This effect is particularly strong during the initial days of exposure and at extreme altitudes. Several factors contribute to this phenomenon:

Hormonal changes: Hypoxia-inducible factors (HIF) and the satiety hormone leptin are elevated at altitude, which can reduce your desire to eat.
Gastrointestinal issues: The gut receives less blood flow as the body prioritizes oxygen for the brain and muscles. This, combined with low oxygen, can slow digestion and cause nausea, bloating, or other stomach discomfort.
Psychological factors: Stress, fatigue, and the cold can also reduce your interest in food, even when you know you need to eat.

This appetite suppression creates a negative energy balance, where your body burns more calories than it consumes. If not managed effectively, this can lead to significant and unhealthy weight loss, compromising your performance and increasing the risk of altitude sickness.

Strategic eating for high-altitude success

To counteract the increased energy needs and suppressed appetite, a proactive and strategic approach to nutrition is essential. The key is to consume small, frequent, and nutrient-dense meals that are easy to digest.

Prioritize carbohydrates: As your body favors carbs for fuel, ensure they make up a significant portion of your intake (around 60%). Good options include whole grains, dried fruits, energy bars, and starchy vegetables.
Include lean protein: Protein is crucial for muscle repair, especially when you're exerting yourself. Pack easily digestible sources like jerky, legumes, or protein powders.
Don't fear healthy fats: Fats are energy-dense and vital for long-term fuel, especially on multi-day treks. Nuts, seeds, and nut butters are excellent, compact choices.
Consume smaller, more frequent meals: Instead of three large meals, aim for 6-8 smaller meals throughout the day. This is easier on your digestive system and helps maintain steady energy levels.

The critical importance of hydration

Dehydration is a major risk factor at altitude and can worsen altitude sickness symptoms. Fluid loss increases dramatically due to:

Increased breathing: The cold, dry air causes you to lose more moisture with every exhale.
Increased urination: The body's initial response to altitude is often diuresis (increased urine production) to help acclimatize.
Suppressed thirst: The sensation of thirst can diminish at altitude, meaning you may not feel thirsty even when dehydrated.

The standard recommendation is to drink an extra 1–1.5 liters of fluid per day at altitude, for a total of 3-4 liters, but needs can vary depending on activity. Plain water is essential, but integrating electrolyte powders can help replenish minerals lost through sweat and diuresis. Avoid excessive caffeine and alcohol, as both can increase dehydration.

Comparison of nutrient needs at sea level vs. high altitude


Nutrient	Sea Level Recommendations	High Altitude Adjustments
Total Calories	Based on individual factors (BMR, activity)	Significantly higher due to increased metabolism and exertion.
Carbohydrates	45-65% of total calories	At least 60% of total calories; prioritize complex carbs for sustained energy.
Protein	10-35% of total calories (or ~0.8g/kg)	Higher intake often required to prevent muscle mass loss (1.2-1.5g/kg or more).
Fats	20-35% of total calories	Similar percentage, but opt for healthy, energy-dense sources like nuts and seeds.
Hydration	~1.5-2L per day	Significantly higher, often 3-4L or more per day, with electrolytes.
Appetite	Natural hunger cues typically reliable	Often suppressed, requiring a proactive strategy to eat consistently.

What to avoid and what to bring

For a successful trip, knowing what foods to pack and what to leave behind is crucial. Avoid heavy, fatty, or highly processed foods that are difficult to digest. Instead, focus on palatable, lightweight, and nutrient-dense options. Pack a variety of snacks to combat potential food aversion. Dried fruit, trail mix, energy gels, and freeze-dried meals can provide essential calories without weighing you down. For longer expeditions, consider consulting a nutritionist to create a tailored plan.

Conclusion

While a reduced appetite might suggest otherwise, you absolutely need to eat more at higher altitude. The body's increased metabolic rate and physiological stress from hypoxia demand a greater caloric and nutritional intake. Overlooking this can lead to weight loss, fatigue, and a higher risk of altitude sickness. By prioritizing carbohydrates, staying hydrated with electrolytes, and eating small, frequent meals, you can effectively fuel your body to adapt and perform, ensuring a safer and more enjoyable experience at elevation. Proactive preparation and listening to your body's signals are key to a healthy and successful high-altitude adventure.

Frequently Asked Questions

Appetite decreases at high altitude due to several factors, including hormonal changes (like increased leptin), reduced blood flow to the gut, and symptoms of mild altitude sickness like nausea.

While individual needs vary, energy expenditure increases at altitude. Some studies show basal metabolic rate can increase by 15-30% initially, with total calorie needs often reaching 3,500-5,000 calories per day for active individuals to avoid weight loss.

A high-carbohydrate diet is generally recommended, as your body uses carbohydrates more efficiently in low-oxygen conditions. While fats are energy-dense, they require more oxygen to metabolize and are harder to digest at altitude.

Yes, dehydration is a major risk factor and can worsen the symptoms of altitude sickness, including headaches and fatigue. Increased fluid intake is critical for acclimatization and prevention.

Good snacks for high altitude are lightweight, nutrient-dense, and easy to digest. Consider trail mix, dried fruit, energy bars, gels, and nut butter packets. Variety is key to combat potential food aversion.

To prevent weight loss, you must consciously increase your caloric intake, even if you don't feel hungry. Focus on easily digestible, carbohydrate-rich foods and eat small, frequent meals to compensate for decreased appetite.

Studies generally agree that for moderate altitudes (up to 5,000 m), nutrient absorption is not significantly affected. Problems arise more from decreased intake and digestive discomfort than from an inability to absorb nutrients.