Too Thin To Breathe Better? Exploring The Association Between Low Bmi and Pulmonary Function in Adolescents and Young Adults Aged 12–30 Years

Abstract

Pulmonary function undergoes substantial development during childhood and adolescence, reaching near-maximal levels during young adulthood. Nutritional status may influence this process, yet research has traditionally focused more heavily on obesity-related respiratory impairment than on the potential consequences of low body weight. This article explores the association between low body mass index (BMI) and pulmonary function among adolescents and young adults aged 12–30 years, with emphasis on developmental differences between adolescents and adults. For individuals aged 12–19 years, nutritional status should be assessed using age- and sex-specific BMI-for-age criteria, whereas BMI <18.5 kg/m² is applicable for adults aged 20–30 years. Available evidence suggests that low BMI may be associated with reduced forced expiratory volume in one second (FEV1), forced vital capacity (FVC), peak expiratory flow and other measures of ventilatory performance, although evidence specifically involving adolescents remains limited and heterogeneous. Potential mechanisms include reduced respiratory and peripheral muscle mass, inadequate energy and protein intake, micronutrient deficiencies, impaired physical development, physical inactivity and underlying chronic disease. The association may also be bidirectional because respiratory and systemic diseases can contribute to weight loss. Comprehensive assessment of nutritional status, body composition, respiratory muscle strength and pulmonary function is therefore warranted in selected individuals with persistent low BMI.