How does the heat index affect your nutrition?

Athletes can and do perform effectively in hot weather, but they can falter when they don't give enough respect to the dangers of heat.
Athletes can and do perform effectively in hot weather, but they can falter when they don't give enough respect to the dangers of heat.

You've probably made a similar evaluation during oppressively warm weather: "It's not so much the heat, but the humidity." The statement, while almost a cliché, recognizes that the temperature reading on a thermostat isn't the only measure of how you feel when Mother Nature bears down. The heat index is a more scientific and precise accounting of the forces that create discomfort or, alternatively, conditions that feel pleasant to the human body.

The heat index uses 25 percent humidity as a baseline. If, for example, it's 100 degrees Fahrenheit (37.78 degrees Celsius) outside and humidity is at 100 percent, you're experiencing the equivalent of a 195 degree day (or 90.56 degrees Celsius) at 25 percent humidity. That's a statistic that gets people's attention and helps them appreciate the dangers of exertion in such an environment -- which is the intent of the heat index.


Hot weather forces your body to work harder and burn more calories [sources: Mirkin; Popke]. Your heart is increasingly called upon to distribute overheated blood to the skin for cooling, the liver and kidneys are taxed to a greater degree, and vital water -- even your muscles are made of more than 70 percent water -- is lost through sweating at a much faster rate [sources: Ryan; Mirkin; Popke].

All of these factors can lead to everything from cramping and nausea to the shutdown of organs, heatstroke and even death [sources: Popke; Weill Cornell Medical College]. Undertrained athletes and the elderly are at particular risk, but the threat of sickness and death is very real, even for fit, elite and professional athletes [sources: Popke; Weill Cornell Medical College].

Click ahead to learn how you can alter your nutrition for optimum health and safe performance in less-than-ideal conditions.

When the human body is taxed by things like hot weather and exercise, it prioritizes its functions. Cooling itself and protecting vital organs takes precedence, while functions such as digesting complex foods become secondary. Likewise, the decisions you make on what to put into your body will dictate how well your body can perform and hold up under these stressful conditions.

Water becomes especially important when the heat index is high. It makes up most of your blood, which distributes oxygen and nutrients throughout your body [source: Ryan]. But as counterintuitive as it might sound, it's possible -- and fairly common -- for inexperienced athletes to drink so much water that they experience hyponatremia, or water intoxication. Drinking in excess of 1,500 milliliters (50.7 fluid ounces) of water in a 60-minute period can lead to the dangerous condition [source: Better Health]. Water flushes vital electrolytes from the body, so hydration using a sports drink that contains sodium and carbohydrates is important [source: Zelman].

Foods high in water content like fruits and vegetables can be valuable before, during and after exercise. Focus on foods that are easily digestible, low in fat and contain carbohydrates and protein. Examples include pasta, bread and fruits. This is not the time for fast food [source: Zelman]. Unfamiliar foods should be experimented with at another time as your stomach may be particularly sensitive. Energy gels are popular because they are easily digested and contain fast-acting carbs and sugars. Many of these gels are designed with the ideal ratio of protein and carbohydrates in mind for an athlete in the midst of high exertion.

Weekend warriors or professional athletes can and do perform effectively in hot weather, but it's also common for them to falter and even hurt or kill themselves when they don't give enough respect to the dangers of heat. Proper nutrition and a health dose of awareness can go a long way.

Related Articles


  • Better Health Channel. "Water -- A Vital Nutrient." (April 16, 2012)
  • Born, Steve. "Less Is Best -- The Right Way to Fuel." (April 15, 2012)
  • Mirkin, Gabe. "Do you burn more calories in hot or cold weather?" March 6, 2005. (April 15, 2012)
  • Popke, Michael. "Georgia Faces Heat, Approves New Hot-Weather Policies." Athletic Business. March 20, 2012. (April 15, 2012)
  • Ryan, Monique. "Daily Hydration Essentionals: Water, The First Nutrient." Apr. 3, 2012. (Apr. 15, 2012)
  • Weill Cornell Medical College. "Seniors Keep Their Cool This Summer and Learn How To Prevent Heat-Related Injuries." April 2012. (April 15, 2012)
  • Zelman, Kathleen, MPH, RD, LD. "What to Eat Before, During and After Exercise." WebMD. (April 15, 2012)