Side Effects of Marathon Running

A record 518,000 people ran a marathon in 2011, according to Running USA. In 2012, cities across the U.S. held 850 marathons, a record high, compared to approximately 300 marathons held in 2000. The increased interest in marathon running should be a good development for a nation that has high levels of obesity, but training for and running 26.2 miles regularly doesn't come without side effects. Although the exercise can help with weight management and improve overall cardiovascular health, some people can suffer negative consequences from pounding the pavement too often.

  1. Enhanced Fitness

    • When someone dies during a marathon, it makes big news. However, instances of death are quite rare -- just 0.75 per 100,000, reported Johns Hopkins in 2012. "Sports Health" published a paper in 2012 noting that this risk is greatly outweighed by the positive side effects of running long distances, including improved quality of life and enhanced longevity. Regular physical activity helps you burn calories and avoid weight gain, maintain muscle mass and keep your heart and respiratory system healthy.

    Injuries

    • When preparing for a marathon, your peak training weeks can include 40 to 100 miles of running. Even if you build up gradually to these intense levels, wear shoes that fit your gait and provide yourself adequate rest, you may still suffer running-related injuries, such as shin splints, plantar fasciitis, Achilles tendinitis and knee pain. A review of the literature published in "Sports Medicine" in 2007 noted that when your training exceeds 40 miles per week, the risk of injury is particularly high. Protect yourself by not increasing your miles too quickly and by resting and stretching adequately during training.

    Compromised Immunity

    • Stress decreases your immune function. Exercise, particularly intense exercise such as racing and hard training, counts as stress on the body. As a result, marathoners are at an increased risk of developing upper respiratory tract infections, according to a paper published in the 2007 issue of “Sports Medicine.” Heavy training causes your body to focus on repairing fatigued and broken-down muscles, which means your body focuses less on bolstering immune cells. This gives bacteria and viruses an opportunity to take hold and make marathon runners sick.

    Iron Deficiency

    • Iron deficiency can lead to fatigue, weakness, headaches, irritability, brittle nails, dizziness, pale skin and shortness of breath. A study in the June 2005 issue of the “Journal of the American Dietetic Association” found that among 121 adults who participated in regular aerobic training weekly, 26 percent of women and 6 percent of men were iron-deficient. Female runners are especially vulnerable -- a 2010 study in the “European Journal of Clinical Nutrition” showed that 28 percent of women recreational marathon runners were deficient in iron. Check with your doctor before supplementing your diet with iron pills, however. Excess iron can cause health problems, too, and men do not often need extra iron nutrition.

    Increased Appetite

    • Marathon runners cover a lot of miles, which means they burn a lot of calories. With this extra activity, your appetite naturally increases. When you are in periods of intense training, you may find yourself hungrier than usual. A study published in a 2009 issue of the "American Journal of Physiology" found this mechanism is stronger in women. Feed your increased hunger with low-calorie nutritious foods, such as fruit and vegetables, to avoid gaining weight. Your body may need more carbohydrates than a person who is not training for marathons because carbs provide fuel for your runs.