A new study has said that apple-shaped women with a waist bigger than 88cm are at increased risk of developing asthma - even if they have a normal body weight.
It is well-known that being overweight raises the risk of asthma but the new study, by the Northern California Cancer Centre at Berkeley, suggests that the amount of weight women carry around the abdomen might be particularly important.
For the study, the researchers analysed data on 88,304 female teachers and school administrators.
Asthma was more than twice as likely in obese women, and more than three times as likely in extremely obese women than in those of normal body weight.
The researchers also found that women of normal body weight, but with a waist circumference of more than 88cm were also at increased risk - around a third higher than those with a smaller waist.
Body mass index (BMI) has been widely used as a standard measure of obesity.
However, some scientists argue that waist circumference may be a more useful measure because it more closely reflects levels of visceral fat deposits found around the body's organs.
Visceral fat is metabolically different from other types of fat found in the body, and may have different - and more profound - effects on health.
"Visceral fat is metabolically more active - it can produce compounds that may cause inflammation. Inflammation may then be related to asthma," the BBC quoted author Julie Von Behren as saying.
The study appears in the journal Thorax.