Beneficial impact of weight loss on respiratory function in interstitial lung disease patients with obesity

Interstitial lung disease (ILD) patients commonly become obese or overweight due to deteriorated daily living activities and the adverse effects of prednisolone. This study aimed to clarify the effect of weight loss on pulmonary function test (PFT) in ILD patients with obesity. Among all consecutive ILD patients with a body mass index (BMI) ≥ 27 kg/m2 who received nutrition education for improving obesity between June 2014 and December 2018, we retrospectively included patients who successfully decreased their body weight by over 2 kg and underwent follow-up PFT within 6 months. The results of PFT at baseline and follow-up and the level of Krebs von den Lungen-6 (KL-6) were compared. Eleven patients (5 men and 6 women; median BMI of 34.1 kg/m2), were enrolled. For PFT at baseline, the percentages of forced vital capacity (%FVC), functional residual capacity (%FRC), and diffusing capacity of the lung for carbon monoxide (%DLCO) were 69.3%, 59.9%, and 54%, respectively. The median KL-6 was 1035 U/mL. The median interval from baseline to the follow-up PFTs was 41 days. Compared to the baseline results of PFT, %FVC, %FRC, and %DLCO significantly increased (p = 0.018, 0.0006, and 0.024, respectively), and the changes in body weight and FVC were strongly correlated (p = 0.0004). In addition, the median serum level of KL-6 at follow-up tended to decrease by 206.5 U/mL (p = 0.083). In ILD patients with obesity, weight loss is important and potentially improves their disease course.