Immediate and long term effects of weight reduction in obese people with asthma: randomised controlled study

Abstract

Objective: To investigate the influence of weight reduction on obese patients with asthma.

Design: Open study, two randomised parallel groups.

Setting: Private outpatients centre, Helsinki, Finland.

Participants: Two groups of 19 obese patients with asthma (body mass index (kg/m(2)) 30 to 42) recruited through newspaper advertisements.

Intervention: Supervised weight reduction programme including 8 week very low energy diet.

Main outcome measures: 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).

Results: 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.

Conclusion: Weight reduction in obese patients with asthma improves lung function, symptoms, morbidity, and health status.

Figure 1

Mean morning premedication values for PEF, FEV₁, and FVC (% of predicted) at different stages during study. Vertical bars show standard errors of the mean. *Change from baseline shows significant (P<0.05) difference between groups (see table for P values)

Figure 2

Mean values for cough and dyspnoea (mm on visual analogue scale) and mean number of daily rescue medication doses at different stages during study. *Change from baseline shows significant (P<0.05) difference between groups (see text for P values)

Figure 3

Health status: mean scores for symptoms, impact, and activity, and mean total scores, according to St George's respiratory questionnaire. *Change from baseline shows significant (P<0.05) difference between groups (see text for P values)