Obesity is a known risk factor for asthma, but few studies have looked at the relationship between abdominal obesity and asthma.
Researchers from the Northern California Cancer Centre studied 88,304 women. The women gave details about their weight, lifestyle and any asthma symptoms.
Obese women were more than twice as likely to have adult-onset asthma as women with a BMI below 25. Extremely obese women were more than three times more likely to have asthma.
The researchers also found that women with waists bigger than 88cm had a risk of developing asthma a third higher than those with smaller waists, even if they had a normal BMI.
Is waist size a reiiable indicator?
This study adds to growing evidence that waist circumference maybe a more accurate measure of obesity than BMI.
The researchers say that this is because it closely reflects levels of visceral fat deposits. Visceral fat is thought to be metabolically active and capable of producing compounds that cause inflammation, which may be related to the increased asthma risk.
The researchers add that rates of abdominal obesity are increasing faster than overall obesity, highlighting the importance of measuring waist circumference.
What do other researchers say?
Leanne Metcalf, director of research at Asthma UK, said that, because the study involved a large number of women, the results were likely to have some significance.
'It is important that people with asthma eat a healthy, balanced diet, which is low in fat and sugar, and take regular exercise,' she said.
'Taking these steps can aid weight loss, improve lung function and help get asthma symptoms under control, especially given the established links between high levels of abdominal fat and other long-term health conditions.'
Dr Noemi Eiser, honorary medical director for the British Lung Foundation, added the research 'reinforces the need for women to lead a healthy lifestyle and be more aware of the health risks of a large waist size'.
- Women with waists bigger than 88cm are more likely to develop asthma.
- Visceral fat build-up appears to increase the risk of asthma by causing inflammation.
- Asthmatics should control their weight to keep their symptoms under control.