Does BMI affect thermal comfort in young people in warm indoor environments? Evidence from a climate chamber experiment in non-normal BMIs

This study aims to investigate the differences in thermal comfort between younger people with lower and higher body-mass-index (BMI) in warm environments. A total of 20 college participants (23.6 ± 0.88 years) were recruited for a climate chamber experiment at air temperatures of 30, 32, and 34 °C. Participants were categorized into two BMI groups: a lower BMI group (17.9 ± 0.63 kg/m²) and a higher BMI group (25.8 ± 0.96 kg/m²). Psychological states—assessed using Restoration Outcome Scale (ROS) and Pleasure, Arousal, and Dominance (PAD) emotion scale—were collected alongside thermal perceptions, including thermal sensation, thermal comfort, and perceived sweating votes (TSV, TCV, and PSV). Additionally, thermal responses, such as skin temperature and wettedness, tympanic temperature, heart rate, and blood pressure (T_skin, W_skin, T_t, HR, and BP), were recorded. The results indicated that the higher BMI group exhibited significantly greater PSV, W_skin, and BP compared to the lower BMI group (p < 0.05), with differences of 0.5–0.8 scales, 0.15–0.3, and 10–28 mmHg, respectively. Path analysis revealed a significant difference in the effects of T_skin, W_skin, and BP on TCV via PSV in the higher BMI group. Psychological factors (PAD and ROS) were found to potentially exacerbate thermal discomfort through TSV and PSV. An optimized two-node model was developed based on adjustments to metabolic rate, skin blood flow, cardiac output, and neutral temperatures. These findings contribute to an understanding of indoor thermal comfort and its assessment for young people with varying BMIs.