[Clinical symptom relief in obese patients with persistent moderate asthma secondary to decreased obesity]. Immediate and long term effects of weight reduction in obese people with asthma: randomised controlled study.
The prevalence of asthma and obesity has increased last years implying important economical and social consequences. A relationship between asthma severity and obesity grade has been found. Therefore, it is necessary to evaluate if obesity decline has a beneficial impact on asthma severity.
                To evaluate the effect of obesity decline on control symptoms and asthma severity.
                Ninety-six patients with obesity and moderate chronic asthma were randomized to group A or B and were maintained for 40 days on a low calorie diet. At baseline and at the end of the study, symptoms, measurement of obesity, spirometry, inflammatory cytokines and immunoglobulin's levels were assessed. Diets' safety was evaluated based on laboratory test. Data were analyzed with Student's t test.
                After 40 days on a low calorie diet, in group A, there were significant decreases of obesity (p < 0.001) and IgE, symptoms almost disappeared (cough persisted in 20%) and medication was suspended in 80%. Group B had obesity decline but IgE levels remained (> 100 UI/mL), symptoms and drug regimen remained unchanged. Both diets were not harmful for patients.
                These results show that asthmatic obese patients maintained for 40 days on low calorie diet A, had obesity and IgE levels decrease and symptoms and asthma severity relief. 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.
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.