Elisabeth Luder

Obesity and Asthma

Obesity and asthma are both common complex traits responsible for substantial morbidity in the developed world. The consistency of the relationship between obesity and asthma, the temporal and dose-response association, and the correlation of obesity with intermediate phenotypes for asthma suggest that the obesity-asthma link is causal. With few exceptions, the existing epidemiological studies show a consistent positive association of obesity with both incidence and prevalence of asthma in children and adults, with the effect being greater in females than in males. Obesity precedes and predicts the development of asthma, not the other way around, and the effect persists after controlling for diet and physical activity. The dose-response relationship is demonstrated by the finding that the greater the obesity the greater the effect on asthma. Studies are showing improvements in asthma in subjects who lose weight. From these observations, the main research issues at present relate to the actual biological mechanisms by which obesity influences the asthma phenotype. The specific areas requiring further investigation are: direct effect of obesity on mechanical functioning of the lung; changes in the immune or inflammatory responses directly or through genetic mechanism; sex-specific influences relating to hormones; and the influence of maternal diet on fetal programming. At present, we still do not have a good understanding of the precise relationship between obesity and asthma.

Obesity and Asthma: Complex Interactions

Asthma and obesity are both chronic diseases and their prevalence has risen in recent years. Given the parallel increase, asthma and its related symptoms and phenotypes have been associated with body mass index (BMI) and obesity. Obesity may directly affect the type and severity (phenotype) of asthma by direct mechanical effects, by enhancing the immune response through related genetic mechanisms, and by sex specific influences such as hormones. Alternatively, obesity may be linked to other environmental factors such as physical activity, diet, and birth weight. These environmental influences, in combination with genetic susceptibility, may then lead to enhanced susceptibility to asthma. The features of these mechanisms are addressed.