Weight Loss Relieves Asthma (September 30, 2007) By Alan R. Gaby, MD

Obese individuals who suffer from asthma may experience a significant improvement in their asthma if they lose weight, according to a study published in this week?s British Medical Journal.1 This finding, which has not been previously reported, represents a potential breakthrough for millions of asthmatics.

In the new study, performed at Helsinki University Central Hospital, Helsinki, Finland, 38 obese adult patients with asthma were randomly divided into two groups. The treatment group took part in an eight-week weight-reduction program, during which time they consumed only about 420 calories per day, in the form of a specially prepared formula diet. The control group continued on their usual diet. During the eight-week diet period, patients in the treatment group lost an average of 31.2 pounds, or 14.5% of their pre-study weight. In contrast, those in the control group lost an average of about two-thirds of a pound.

Standard tests of lung function (forced expiratory volume in one second [FEV1] and forced vital capacity) were performed in all patients at the start of the study and at the end of the eight-week program. The results showed a statistically significant improvement in lung function in the treatment group compared with the control group. In addition, individuals in the weight-loss group experienced a significant improvement in shortness of breath and required significantly less rescue medication, compared with those in the control group.

Asthma is a lung disorder in which spasms of the bronchial passages restrict the flow of air in and out of the lungs. Symptoms include coughing, wheezing, and difficulty breathing. Many asthmatics suffer only mild symptoms, but others experience asthma ?attacks? which can be severe enough to require hospitalization, or may even be fatal. More than 17 million Americans?about one in 16 people?have asthma, and the prevalence of this lung disorder is increasing. Between 1980 and 1994, the number of people with asthma grew by 75%.2 While many experts believe that indoor and outdoor air pollution are contributing to the rising prevalence of asthma,3 other factors are most likely involved, as well. Obesity is also becoming increasingly common in the United States; between 1991 and 1998, the prevalence of obesity increased from 12.0% to 17.9%.4 While excessive body weight is not commonly considered a cause of or a triggering factor for asthma, obesity has been found to have adverse effects on lung function5 and, in preliminary research, the risk of asthma has been reported to increase with increasing body weight.6 Therefore, weight loss may be beneficial for overweight asthmatics.

Interestingly, the published study reports that the patients in the treatment group maintained most of their weight loss long after the program was terminated. One year after the start of the study, these individuals were still, on average, 24.4 pounds below their pre-study weight. In the control group, on the other hand, patients weighed about five pounds more after one year than they did at the start of the study. Equally important, the improvements in lung function that were noted in the weight-loss group after eight weeks were still evident after one year. In addition, overall health status, as determined by a clinical questionnaire, was significantly better after one year in the weight-loss group than in the control group.

This study demonstrates that, in obese people with asthma, losing weight can improve lung function, symptoms, and overall health. While it is not clear how weight loss brings about these improvements, there are several possible explanations. First, weight loss appears to have a direct influence on the mechanics involved in the opening and closing of airways during breathing. Second, being overweight around the abdomen tends to aggravate gastroesophageal reflux (the regurgitation of stomach contents into the esophagus),7 which can be a contributing factor to asthma.8 When obese people lose weight, they may experience a reduction in ?acid reflux? and a resulting improvement in their asthma. Third, individuals who are overweight require more energy and more oxygen during exercise. Losing weight may therefore reduce the workload and, consequently, the symptoms of asthma during exercise. Fourth, studies have shown that there is a psychological component to asthma.9 Obese people who have successfully lost weight tend to feel better about themselves, which may lead to a lessening of their asthma symptoms.

Another possible explanation for the improvement is that the special weight-loss diet used in this study may have restricted the intake of certain common food allergens. Although the role of food allergy in asthma remains controversial, unrecognized allergy to frequently consumed foods (such as wheat and dairy products) has been reported to be a contributing factor in many cases.10 11 On the other hand, if reduced intake of allergenic foods played a major role in the improvement seen in the Helsinki study, one would have expected asthma symptoms to worsen after the patients resumed their usual diet. In fact, the benefits persisted for many months after the special diet was discontinued, suggesting that weight loss per se, as opposed to dietary modification, was responsible for the results.

Although additional research needs to be done, this study offers new hope, and should provide additional incentive for overweight asthmatics to bring their weight down to a level that will promote better health.

Source:

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Alan Gaby, MD, an expert in nutritional therapies, is the Contributing Medical Editor of the Townsend Letter for Doctors. He served as a member of the Ad-Hoc Advisory Panel of the National Institutes of Health Office of Alternative Medicine. He is the author of B6: The Natural Healer (Keats, 1987), Preventing and Reversing Osteoporosis (Prima, 1994), and The Patient?s Guide to Natural Medicine (Prima, 2000), and co-author of The Natural Pharmacy, 2nd Edition (Healthnotes, Prima, 1999), the A?Z Guide to Drug-Herb-Vitamin Interactions (Healthnotes, Prima, 1999), and The Patient?s Book of Natural Healing (Prima, 2000). He is currently the Endowed Professor of Nutrition at Bastyr University, Bothell, Washington.