MedWire News: Obese people with asthma tend to experience more severe breathing difficulties during an asthma attack than their thinner counterparts, results of a US study show.

The findings suggest that obese asthma patients can reduce their asthma severity by losing weight, and add to the growing list of health benefits associated with maintaining a healthy weight.

Professor D Robin Taylor and colleagues from the University of Otago in Dunedin, New Zealand studied 30 women with asthma aged between 20 and 60 years. The patients were divided into normal weight, overweight and obese groups based on their body mass index.

All the participants underwent lung function tests before and after they were asked to breath in a substance, called methacholine, known to cause asthma attacks. This was performed under controlled conditions in a laboratory setting.

The team found that airway constriction was significantly more severe in the obese patients after breathing methacholine than in the other two groups. This means that obese patients found it significantly more difficult to breath after exposure to the chemical than the other patients.

"We know that asthma in obese subjects is more likely to persist and is more likely to be perceived to be severe. These individuals often require more treatment to achieve asthma control," said Professor Taylor.

He concluded: "Our study provides an insight into why this might be happening - the same asthma 'trigger' produces a greater effect in obese individuals."

The research is published in the American Journal of Respiratory and Critical Care Medicine.