Human thermoregulation and obesity

On average 80% of muscular physical activity energy has to be released by the body as heat. Obese people have a thick insulating fat layer. We investigated whether the concomitant thermal isolation can fundamentally limit heat dissipation and therefore exercise capacity in the obese. To estimate key values of thermoregulatory properties in humans, relevant mechanisms, models, their parametrization and data that were taken from the literature. Investigated thermoregulatory relevant properties and mechanisms included body heat capacity, clothing, sweating, vasodilation, respiratory evaporation, and body thermal resistance. We found that the most effective mechanisms for heat loss during exercise are vasodilation (increased tissue conductance) and sweating. Thermal insulation by the fat layer is effectively shunted by increased skin blood flow. Since muscle and skin compete for blood flow for energy supply and heat transport, respectively, we hypothesize that cardiac output and tissue/muscle blood flow are m...