Promoting weight loss in asthma

The world is in the midst of an unprecedented obesity epidemic. With this epidemic has come a major shift in the type of diseases commonly encountered in medical practice, for example type II diabetes (once a disease of the overweight elderly patient) is now affecting children. We are only just beginning to understand the impact obesity has on pulmonary health.¹ Obesity is a major risk factor for asthma, and leads to poor asthma control which does not respond as well to therapy as asthma in lean asthmatics.² The “Tenor” study, a survey study to identify characteristics of patients with severe asthma, found that over 50% of adults with poorly controlled asthma in the United States were obese.³ There is an urgent need to develop therapies specifically targeting obese asthmatics, who often represent the majority of severe asthmatics seeking medical care in the 21^st Century.

Obesity is a risk factor for the development of asthma and poor asthma control, so one obvious intervention that might improve asthma control is weight loss. Uncontrolled studies in bariatric surgery suggest dramatic improvements in asthma control with weight loss surgery.^4,5 Bariatric surgery is an expensive, complex procedure associated with morbidity and even mortality, and so is unlikely to have a significant public health impact on asthma. More modest weight loss can be achieved with lifestyle interventions, and there have been a few such studies in asthmatics. The published studies in adults suggest that a weight loss of 5-10% is required to produce a significant improvement in asthma control.^6-10

This degree of weight loss is similar to that required to improve metabolic and cardiovascular parameters,¹¹ but while there is a long history of studying weight loss in the context of cardiovascular disease and diabetes, only recently has this been considered for asthma. Achieving weight loss is challenging and labor intensive, and has received little attention as part of the management of patients with asthma. There is very limited medical literature to guide us on weight loss interventions in asthma, indeed a recent Cochrane review noted that there was insufficient data to support weight loss as a therapy in asthma;¹² this lack of data likely reflects the challenge of studying this type of intervention. However, to manage the asthma patient population in this day and age, it is critical to understand how to promote effective life-style interventions to achieve weight loss. There may be unique challenges faced by the asthmatic population, who may have disease-related difficulties with exercising, fears related to exercising, and perceive that their medications promote weight gain. Strategies to promote successful weight loss in asthmatics are needed and these must be simple enough to disseminate into clinical practice.

The study by Scott et al in this issue of the journal is timely and important, as it provides important insights into factors that predict successful weight loss in asthma.¹³ The authors report on factors that predict successful weight loss in a randomized controlled trial. Their results can be used to guide trials of weight loss in asthma, and strategies to manage patients in clinical practice. As previously reported, participants were randomized to one of three intervention groups: an exercise group, a low calorie diet group, and a combined low calorie and exercise group. Participants randomized to the exercise and diet, and the diet alone group, both lost a significant amount of weight and this was associated with improved asthma control.⁷ In the current paper, the authors found that male participants lost more weight than female participants; the reasons for this are not clear, but may be related to higher metabolic demands in men facilitating weight loss. Gender specific interventions may be required to produce successful weight loss in women with asthma. Indeed, the authors found that improvements in emotional eating, and uncontrolled eating correlated with weight loss in women, whereas an increase in cognitive restraint related to eating predicted weight loss among men. This suggests that sex-specific strategies may be important to successfully induce weight loss in overweight and obese patients with asthma.

A fascinating result was that those who had worse asthma, as measured by asthma quality of life, lost significantly more weight. Those with more severe airflow limitation, and worse asthma control also tended to lose the most weight. This is encouraging for those caring for obese patients with uncontrolled asthma, as it suggests that those with more severe asthma are most likely to lose weight. Theories of behavior change¹⁴ suggest that clinicians may be able to induce the motivation of their patients to change behavior by discussing the deleterious effects of obesity on asthma control and providing information on the positive effects of weight loss. Such discussions can create a teachable moment (Lawson et al)¹⁵ and begin the process of moving asthma patients toward successful weight loss..

The treatment of asthma has largely focused on use of drugs rather than life-style changes. However, available therapies have been developed for the treatment of lean asthmatics, and these medications are less effective in obese asthmatics. Weight loss is an attractive goal that might improve asthma outcomes in obese patients with asthma. There is an urgent need to develop effective lifestyle interventions that can successfully induce weight loss in obese asthmatics if we are to effectively intervene in the current epidemic of poorly controlled asthma. The study by Scott et al provides important insights that will drive future research and clinical care.