A number of studies have shown an association between obesity and asthma, both of which have become much more common over the past three decades. A team of doctors at the Palo Alto Medical Research Institute in California looked at about 4,500 men and women from the National Health and Nutrition Examination Survey for 2005-2006. About a third of the participants were overweight, and another third were obese. Forty-one percent had some type of allergy, while 8 percent had asthma. Twelve percent of the obese individuals had asthma, compared to six percent of the normal-weight study participants. The likelihood of asthma rose as the body mass index — BMI, a relation of weight and height used to gauge obesity — increased and waist circumferences expanded. The risk of asthma was more than tripled for the most obese individuals compared to normal weight people. The reason why the two might be related is still not clear. Some researchers have suggested the system-wide, low-grade inflammation that occurs with obesity may be a factor, while others have argued that resistance to the key blood-sugar-regulating hormone insulin — which rises with excess weight — is the reason for the link. Obesity was independently associated with asthma after controlling for insulin resistance and socio-demographic factors. For access to an abstract of the article published in Allergy, please click here.