Become a Member

Get access to more than 30 brands, premium video, exclusive content, events, mapping, and more.

Already have an account? Sign In

Become a Member

Get access to more than 30 brands, premium video, exclusive content, events, mapping, and more.

Already have an account? Sign In


Race Fueling

How to Fuel When Training and Racing at Altitude

Training at altitude requires extra attention to your nutrition.

Lock Icon

Become a member to unlock this story and receive other great perks.

Already have an Outside Account? Sign in

Outside+ Logo

Intro Offer
$3.99 / month*

  • A $500 value with everything in the Print + Digital Plan plus 25+ benefits including:
  • Member-only content on all 17 publications in the Outside network like Outside, Better Nutrition, VeloNews, and more
  • Outside Learn, our new online education hub loaded with more than 2,000 videos across 450 lessons including 10 Weeks to Your Best 70.3 and the 60 Day Metabolic Reset
  • Download your personal race photos from FinisherPix* for one race (up to a $100 value).
  • Member-only newsletter, and event meet and greets with editors
  • Get up to $30 off your next race and $30 off race fees every year you are a member through AthleteReg*
  • Annual gear guides for cycling, running, skiing, training, and more
  • Annual subscription to Outside magazine
Join Outside+

Digital + Print
Intro Offer
$2.99 / month*

  • Annual subscription to Triathlete magazine
  • Access to all member-exclusive content on
  • Ad-free access to
Join Triathlete

*Outside memberships are billed annually. Print subscriptions available to U.S. residents only. You may cancel your membership at anytime, but no refunds will be issued for payments already made. Upon cancellation, you will have access to your membership through the end of your paid year. More Details

This article originally appeared in the September 2015 issue of Triathlete.

Many athletes choose to live and train at high altitude with the particular goal of increasing endurance performance. While the merits of altitude training and the best methods and timing of implementation can be debated, let’s focus on changes in nutritional demands at higher elevations.

It is clear that any competition at altitude will benefit from acclimatization, or adaption to changes in physiological and metabolic demands. Systems that react to altitude and changes in oxygen pressure include cardiovascular, pulmonary and endocrine and the central nervous system, meaning changes in resting and maximal heart rate, rates of ventilation, blood pressure, VO2 max and oxygen transport. Nutritional support of these adaptations and systems during altitude acclimatization is crucial.

RELATED: Altitude Acclimation: 5 Tips for Optimizing Performance

As with any environmental condition, there is a range of nutritional demands. A mildly warm day will require different nutritional strategies as compared with one of searing heat and humidity; similarly, with rising altitude there will be greater effects. For the most part, when endurance athletes talk of moderate altitude, they are talking somewhere in the range of 5,000 to 8,000 feet (1,500-2,500 meters).

Here are some nutritional challenges athletes might face at moderate altitude.


Extra fluid intake is vital. Rising altitude means that breathing is shallower and more frequent; this increased ventilation along with dry air leads to greater fluid losses through the respiratory system. Additionally, sweat evaporates quickly, which can lead you to believe you are not losing much fluid and are less inclined to drink. When training or competing at altitude, carry more fluid than you would regularly and keep drinking to avoid dehydration. Even on shorter runs that you would complete at sea level without water, it is a good idea to use something such as a hydration belt or a handheld quick draw when training at altitude; you are more likely to drink often when fluid is readily available.

RELATED: Are You Doing Thirst Right? The Science Says Probably Not

Fuel utilization

Basal metabolic rate (BMR) increases at altitude, especially in the first couple of days. Appetite is also suppressed by hypoxia, so to minimize reduction in body mass and loss of muscle, take care to match your caloric needs. With time to acclimatize, BMR drops again, but not quite to base level (sea level rate). There also seems to be a shift in fuel utilization toward a greater reliance on carbohydrate as opposed to fat stores. If flying in for a race, you might consider frequent small meals that are carbohydrate-rich to maintain energy levels. Carbohydrate-rich sports drinks would also be beneficial in meeting both increased fluid and carbohydrate needs.

Iron stores

As the body tries to adapt to a lower oxygen concentration in the air, greater numbers of red blood cells, which transport oxygen to working muscles, are produced by the bone marrow. In fact, this is the primary reason why endurance athletes train at altitude; to achieve the increase in oxygen-carrying capacity and the associated improvements in endurance capacity. However, iron is required to manufacture hemoglobin (the oxygen-binding portion of red blood cells) and consequently, any iron deficiency can reduce the benefits of altitude training. Before you go to altitude, consider having a blood test to ensure your iron stores are adequate. Talk to your doctor about your plans to train or race at altitude and if you should consider taking iron supplements. Otherwise, include iron-rich foods in your diet (animal sources such as lean red meats are best absorbed).

RELATED: How to Optimize Your Iron Levels – Besides Just Eating Red Meat

Immune stress

Altitude places stress on the body, which might affect your immune system when combined with hard training. A diet rich in natural antioxidants is perhaps even more important to help the body cope, adapt and stay healthy. Along with a healthy diet, good hygiene habits and plenty of recovery will also help.

Other factors

Often altitude goes hand in hand with either hot, dry climates or cold conditions. Keep this in mind when it comes to changing nutritional needs.

Remember, too, that individuals adapt to altitude differently. Take your time, listen to your body and don’t expect to feel great in the first few days or even up to two weeks.

RELATED: Dear Coach: What are the Benefits and Pitfalls of Training at Altitude?

Altitudes around the world

Location Height (in feet)
Boulder, CO 5,430
Bend, OR 3,628
Santa Fe, NM 7,000
Lake Tahoe, NV 6,225
Mexico City, Mexico 7,350
Font-Romeau, France 6,070
Albuquerque, NM 5,280
Denver, CO 5,280
Missoula, MT 3,209
St. Moritz, Switzerland 6,090
Flagstaff, AZ 6,910
Sierra Nevada, Spain 7,610
Mt. Teide, Tenerife 6,200
Iten, Kenya 8,000
Mt. Kilimanjaro, Tanzania 19,298
Mt. Everest, Nepal 29,028