The study, led by Robert Podstawski and colleagues, examined how body mass index (BMI) affects body mass loss (BML) in young, sedentary individuals exposed to thermal stress in a dry sauna. Conducted on 674 students (326 women and 348 men) aged 19-20, the study aimed to identify the relationship between BMI and BML induced by sauna use. Participants underwent two 10-minute sauna sessions with a 5-minute break in between, while their body weight was measured before and after each session. The results showed that individuals with higher BMI, particularly those who were overweight or obese, experienced greater body mass loss during sauna exposure. Conversely, underweight participants exhibited the least amount of BML. The study also developed equations to help estimate fluid loss during sauna use, emphasizing the importance of hydration, especially for individuals with higher BMI.
The researchers found that the amount of body mass lost in the sauna varied depending on BMI, with individuals in the overweight and obese categories losing more weight than those in the underweight or normal weight groups. This BML was particularly pronounced in males and females with higher BMI values. While the correlation between BMI and BML was not linear, the study established formulas for estimating BML based on BMI, highlighting a direct relationship where changes in BMI influenced BML. The findings suggest that while sauna use may lead to temporary body mass reduction, it should be used cautiously by those with higher BMI, due to the increased risk of dehydration. The research, conducted at the University of Warmia and Mazury in Poland, provides insight into how sauna bathing can affect body mass and fluid loss, particularly in sedentary individuals.
