The effect of obesity on lung function in children stratified by asthma status is not fully elucidated. We evaluated the impact of adiposity indices, including Body Mass Index (BMI) and estimated fat mass (eFT), on lung changes in asthmatic and non-asthmatic children with rhinitis.

We performed a retrospective review of 400 pediatric patients, classified into an asthma group (n = 200) and a no-asthma group (n = 200). According to the BMI z-score all subjects were classified into normal-weight patients (NW; −2 ≤ BMI z-score <1) and overweight patients/patients with obesity (OW/OB; BMI z-score ≥1). Lung function parameters were measured by spirometry. BMI and eFM were considered as adiposity indices.

Excess weight/obesity was present in 37 % of patients. The OW/OB group showed higher basal forced expiratory vital capacity (FVC) and lower forced expiratory volume in 1 s (FEV₁), FEV₁/FVC ratio compared to the NW group (p ≤ 0.01). FVC and FEV₁ were correlated with the BMI z-score, and FEV₁/FVC with eFT (p ≤ 0.01). No differences were noted between the NW and the OW/OB groups in terms of respiratory parameters except for FVC (p < 0.01). In the OW/OB group, asthma patients were significantly different based on FEV₁, FEV₁/FVC, and forced expiratory flow at 25–75 % of FVC (FEF_25/75) (p < 0.01). The BMI z-score was correlated with FVC and FEV₁ in both the no-asthma and asthma groups (p ≤ 0.01 and p ≤ 0.05, respectively), while eFM was correlated with FEV₁/FVC (p = 0.007) in the asthma group only.

Obesity seems to have a significant impact on lung function in children with respiratory allergic diseases. BMI and eFM may be used to evaluate the impact of adiposity on lung function.