Both excessive thinness and severe obesity are associated with impaired immune responses.1 Obesity increases the risk of infection, at least in hospitalised patients, according to preliminary research.2 However, these effects may not occur with mild to moderate obesity in otherwise healthy people, and attempts to lose weight through dietary restriction may actually be harmful to the immune system.3 The detrimental effects of both appear to be offset when people regularly perform aerobic exercise.4, 5
The effects of exercise on immune function depend on many factors, including frequency and intensity of exercise.6 Regular moderate physical activity has positive effects, at least on some measures of immunity, and has been shown to reduce risk of upper respiratory infection. However, very intense and prolonged exercise, such as running a marathon or overtraining, can, in the short term, actually increase the risk of developing infections.7 The positive effects of moderate exercise on immunity may also partly explain the apparent reduced susceptibility to cancer of physically active people.8
The immune system is suppressed during times of stress. Chronic mental and emotional stress can reduce immune function, but whether this effect is sufficient to increase the risk of infection or cancer is less clear.9, 10 Nevertheless, immune function has been increased by stress-reducing techniques such as relaxation exercises, biofeedback, and other approaches,11, 12 although not all studies have shown a significant effect.13
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The information presented by TraceGains is for informational purposes only. It is based on scientific studies (human, animal, or in vitro), clinical experience, or traditional usage as cited in each article. The results reported may not necessarily occur in all individuals. Self-treatment is not recommended for life-threatening conditions that require medical treatment under a doctor's care. For many of the conditions discussed, treatment with prescription or over the counter medication is also available. Consult your doctor, practitioner, and/or pharmacist for any health problem and before using any supplements or before making any changes in prescribed medications. Information expires December 2020.