Depending on an individual's age and body weight, 300 to 500 calories can be burned in a 30-minute steam sauna session. Most health care professionals believe that the weight loss is due primarily to water lost from perspiration, which may not be permanent.
The steam and extreme temperature of 185 degrees Fahrenheit in a sauna cause body heat to rise and skin to perspire. The heat also raises metabolism, increasing the heart rate 20 to 30 percent or more. Saunas may be able to burn as many calories as a three-mile run, but this is likely water weight that can be gained back quickly and easily. Heart patients should check with their doctors before using a sauna.