Gender disparities in thermoregulatory exergy efficiency across the BMI spectrum: Insights from a four-layer human thermal model

Introduction Human energy metabolism is irreversible; some chemical exergy from nutrient oxidation is lost, while other losses imply adjustable inefficiencies. Various public health issues in India affect exergy destruction and metabolic inefficiencies. Objective Hypothesis This study proposes that internal exergy destruction is elevated at both extremely low and high BMI levels, but A normal BMI improves internal exergy efficiency and supports coordinated physiological activity by establishing an optimal thermodynamic state. By evaluating internal exergy destruction and efficiency at various BMI levels, it also aims to assess sexual dimorphism in thermodynamic performance. Methodology A four-layer concentric cylindrical model was developed for computational modelling of virtual 50th-percentile Indian Adults across seven BMI levels (15.0–35.0 kg/m 2 ), using DXA-based Indian anthropometric data. Resting metabolic rate, ATP production, and ATP efficiency were estimated using Indian-specific metabolic equations. Results The internal exergy degradation exhibited a U-shaped pattern associated with BMI, minimising at BMI 22.0 kg/m 2 and rising in underweight and obese circumstances. Males had higher absolute internal exergy destruction at equivalent BMI due to greater metabolic exergy input from body mass and muscle fraction, while females had slightly higher fractional losses due to lower exergy availability and greater adiposity-driven thermal irreversibility. Conclusion These findings, derived from a computational model using virtual representative individuals, suggest that using BMI- and body-composition-based exergy measurements to assess metabolic and thermodynamic health can be helpful, as elevated exergy irreversibility. This may, with future clinical validation, serve as thermodynamic metabolic markers, and can be a tool in diagnosing possible lifestyle diseases.