DOES DIETING IMPROVE ASTHMA CONTROL?

HELSINKI, FINLAND-- Weight loss should be added to the management strategies for asthma, a new Finnish study indicates.[1] In obese patients with asthma, weight reduction improves health status and lung function.

"Supervised weight loss in asthma patients not only reduces symptoms, but it may also lower the need for medications," said Dr. Brita Stenius-Aarniala, lead author of the study.

WEIGHT WATCHING

Weight loss has been shown to improve lung function in the general population of obese persons, and there have been anecdotal reports of symptom improvement among obese asthma patients who lost weight. Thus, Dr. Stenius-Aarniala and colleagues from the department of medicine at Helsinki University sought to determine how it would benefit asthma patients specifically. They studied 38 obese asthma patients, half of whom (the treatment group) participated in a supervised 14-week weight loss regimen and a year-long asthma education program. Study subjects had a body mass index of 30 to 42 and were age 18 to 60 years. The control group underwent only the asthma education program.

By the end of the program, subjects in the treatment group had lost a mean 14.5% of their pretreatment weight; after one year, their mean weight loss was 11.3%. The control subjects experienced no significant weight changes during the education program and gained a mean of 2.2% of their pretreatment weight during follow-up.

WEIGHING THE BENEFITS

Forced expiratory volume in one second (FEV1) and forced vital capacity (FVC) increased following weight loss in the treatment group but decreased in the controls. These differences remained significant at one year. Peak flow increased in the treatment group, although the improvement did not reach statistical significance. The researchers believed this improvement was important nonetheless.

Weight loss initially reduced dyspneic symptoms and use of rescue medications (inhaled bronchodilators) in the treatment group, but these differences did not persist until the study's end. Another benefit of weight loss was an overall improvement in the patients' perception of their health status, as measured by three separate scales. This improvement lasted for the duration of the study.

During follow-up, 16 patients in the treatment group and 18 controls experienced at least one asthma exacerbation. Ten of the patients who lost weight and 13 controls needed one or more courses of oral corticosteroids. The median number of corticosteroid courses administered was one in the treatment group and two in the control group.

Figure 1 Mean Changes in Lung Function After Weight Loss

Data extracted from Stenius-Aarniala et al. BMJ. 2000. [1]

PUTATIVE MECHANISMS

The study authors offer several explanations for why weight loss improves symptoms of asthma:

• In asthma patients, airway obstruction causes early airway closure during expiration. Obesity may accentuate this early closure, especially when a patient is supine. In contrast, weight reduction may delay airway closure during expiration, thereby increasing FEV1 and FVC.
• Weight loss lowers the exercise load, which may alleviate asthma symptoms during exertion.
• A reduction in the amount of abdominal fat may decrease the risk of gastroesophageal reflux, which can worsen asthma symptoms.
• The psychological benefit of weight loss may also have a positive effect on asthma symptoms.

WHY DID THIS PROGRAM WORK?

In an interview with RESPIRATORY REVIEWS, Dr. Stenius-Aarniala suggested that she and her colleagues were able to obtain good weight loss results in the treatment group because their program included both supervision and group support. She noted that most people cannot lose weight on their own, even when told to do so by their doctors.

Dr. Stenius-Aarniala believes further studies will prove that weight loss lowers the need for medications--including corticosteroids--in asthma patients.

"If the need for medication can be reduced, the cost of asthma treatment is lowered; further cost reductions may follow because people of normal weight generally have a lower morbidity rate than obese people do," she commented. These reductions in morbidity and cost will more than offset the cost of a supervised weight loss program, she added.

--Kimberly C.G. Jones

Reference
1. Stenius-Aarniala B, Poussa T, Kvarnström J, et al. Immediate and long term effects of weight reduction in obese people with asthma: randomised controlled study. BMJ. 2000;320:827-832.