Immediate and long term effects of weight reduction in obese people with asthma: randomised controlled study. Prospective controlled evaluation of the effect of a community based asthma education centre in a multiracial working class neighbourhood.
To investigate the influence of weight reduction on obese patients with asthma. Design: Open study, two randomised parallel groups.
                Private outpatients centre, Helsinki, Finland.
                Two groups of 19 obese patients with asthma (body mass index (kg/m(2)) 30 to 42) recruited through newspaper advertisements.
                Supervised weight reduction programme including 8 week very low energy diet.
                Body weight, morning peak expiratory flow (PEF), forced vital capacity (FVC), forced expiratory volume in one second (FEV(1)); and also asthma symptoms, number of acute episodes, courses of oral steroids, health status (quality of life).
                At the end of the weight reducing programme, the participants in the treatment group had lost a mean of 14.5% of their pretreatment weight, the controls 0.3%. The corresponding figures after one year were 11.3% and a weight gain of 2.2%. After the 8 week dieting period the difference in changes in percentage of predicted FEV(1) from baseline in the treatment and control groups was 7.2% (95% confidence interval 1.9% to 12.5%, P=0. 009). The corresponding difference in the changes in FVC was 8.6% (4. 8% to 12.5%, P<0.0001). After one year the differences in the changes in the two groups were still significant: 7.6% for FEV(1) (1. 5% to 13.8%, P=0.02) and 7.6% for FVC (3.5% to 11.8%, P=0.001). By the end of the weight reduction programme, reduction in dyspnoea was 13 mm (on a visual analogue scale 0 mm to 100 mm) in the treatment group and 1 mm in the control group (P=0.02). The reduction of rescue medication was 1.2 and 0.1 doses respectively (P=0.03). After one year the differences in the changes between the two groups were -12 for symptom scores (range -1 to -22, P=0.04) and -10 for total scores (-18 to -1, P=0.02). The median number of exacerbations in the treatment group was 1 (0-4) and in the controls 4 (0-7), P=0.001.
                Weight reduction in obese patients with asthma improves lung function, symptoms, morbidity, and health status. Previous work has indicated a high rate of non-attendance at hospital based clinics among young, multiracial asthmatic patients of lower socioeconomic class. The efficacy of delivering asthma education from a community health centre established in a multiracial working class neighbourhood was evaluated.
                A prospective controlled study was performed in which asthmatic subjects aged between two and 55 years attending a hospital emergency room with acute asthma and living within a defined geographical area of high emergency room users were randomised to the usual follow up or the education centre plus usual follow up. Measurements were taken at entry into the study and again nine months later.
                At nine months patients randomised to the education centre had more preventive medications, more peak expiratory flow meters and better flow meter technique, more self-management plans, better knowledge of appropriate action to take when confronted with worsening asthma, less nocturnal awakening, and better self-reported asthma control than the control group. There was no difference between the study groups in measurements of compliance, hospital admission, days lost from school or work, or emergency room use.
                The main effects of education were on asthma knowledge and self-management skills, whilst improvements in asthma morbidity were small. Potential reasons for this include heterogeneous study population (in terms of baseline self-management skills, asthma severity, ethnicity and age), pragmatic study design, insensitivity of many of the measurements of morbidity, the modest effectiveness of a single time limited education programme, and inability to limit the effects of such a large community based study to the intervention group (there was a 67% reduction in asthma admissions during the study period from the geographical area targeted compared with a 22% reduction for the rest of Auckland).
Implications for practice  
This review found one randomized trial that showed that weight loss may be beneficial for improving asthma control in overweight and obese patients, in conjunction with weight loss in intervention groups in the short term. Applying the GRADE system to the results of this review however, shows that the quality of evidence is low, because although all four studies are RCTs there were serious methodological limitations in the studies (unclear risk of selection bias and high risk of detection bias) and imprecision (small sample size). There is inadequate evidence to comment on the effect of weight loss interventions on quality of life and health care utilization. In addition, there was inadequate reporting of data on adverse effects to permit proper balancing of harms and benefits of the interventions. On account of this low quality of evidence, the benefit of weight loss as an intervention for asthma control remains uncertain, and as such, clinicians should be prepared to help patients to make a decision that is consistent with their own values.

Implications for research  
The finding that most of the included studies were of low methodological quality highlights the need for further well designed RCTs, with emphasis on adequate methods of allocation sequence generation as well as allocation concealment and longer follow-up periods. These studies need to report more fully on relevant outcomes (both statistically significant and otherwise) such as: asthma symptoms/control, use of rescue medication, change in lung function parameters (actual mean/median values), hospital utilization, quality of life, and adverse effects. There is also a need for longer intervention as well as follow-up durations to evaluate the effect of sustained measures to achieve weight loss, and to determine if these effects are still significantly present after a considerable period of time.
There is also a need for these well designed studies in children and adolescents, as well as in low-income countries such as Africa, where the prepackaged, low energy diets, as well as structured physical activity-based interventions utilized in these included studies, may not be feasible or applicable.