Wider waists and asthma risk

Women with extra fat around their waists are more likely to develop asthma, even if they aren't overweight.

Researchers studied 88,304 women teachers in California to examine the relationship between prevalence of asthma with measures of abdominal obesity and adult weight gain. The same association between obesity and increased incidence of asthma was found as in older studies. But it also found a 37 percent increased incidence of asthma among women with a waist circumference of 88 centimetres - about 34 inches - even if they were of normal weight.

Using the standard designations of "overweight" for a woman with a body-mass index (BMI) of 30 or higher and "extreme obesity" for a body-mass index (BMI) of 40 or higher, the study found a doubled incidence of asthma among the obese women and a more than tripled incidence among the extremely obese. While the study was not designed to determine why the location of body fat could play a role in development of asthma, the researchers explained that the waist size can be an indicator of the type of body fat. Abdominal fat is visceral fat, which is biologically more active, and could be acting in some inflammatory way. It has been linked to diabetes and heart disease.

While one conventional explanation is that body fat puts a squeeze on airways, some previous studies have pointed toward the composition of body fat as a possible element in asthma risk. Despite the cause of this link not being clear, the association with asthma provides another reason not to put on extra weight.