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Asthma is an airway condition characterized by inflammation and reversible bronchospasm that affects millions of Americans. Obesity, another common disorder among Americans, is defined by a body mass index of 30 or greater. In the past two decades, there has been a significant increase in the prevalence of both asthma and obesity worldwide. Are the two disorders related to each other?

How is obesity defined?

What is body mass index?

There are several mechanisms by which obesity could cause either respiratory symptoms or more fundamental changes in the airways leading to asthma. In obese people symptoms of breathlessness and wheeze may be due to increased work of breathing. Alternatively, obesity may have a direct effect on the mechanical behaviour of the respiratory system by altering lung volume, airway calibre, or respiratory muscle strength. On the other hand, factors associated with asthma could lead to an increase in obesity. Inactivity or inability to exercise in asthmatic subjects could cause weight gain. Medication required for treatment of severe asthma such as oral steroids may cause weight gain, which may cause asthmatic patients to become obese or to worsen pre-existing obesity.

Articles suggesting a relationship between asthma and obesity

Obesity is a risk for asthma and wheeze but not airway hyperresponsiveness. Schachter et al. Thorax. 2001 Jan;56(1):4-8. Body mass index and asthma in adults in families of subjects with asthma in Anqing, China. Am J Respir Crit Care Med. 2001 Nov 15;164(10 Pt 1):1835-40. The FEF25-75/FVC ratio is associated with methacholine airway responsiveness. The normative aging study. Litonjua et al. Am J Respir Crit Care Med. 1999 May;159(5 Pt 1):1574-9.

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	Date last updated July 26, 2004