By it’s nature, a regular daily yoga practice can create weight loss. Many of the poses work to bring balance to the endocrine and digestive systems, supporting weight loss. The classical sun salutation, for example works every system within the body, increasing strength, flexibility and endurance. I’ve had many students, over the years, who changed their bodies through daily practice. A moderately heated room (80 F) is enough the warm the body and increase flexibility in a safe way. Producing sweat during asana practice is a good thing – purification through heat.
The main problem with a heated room for yoga practice or any exercise is that if the body can not cool it self through sweating core temperature rises, the heart rate and blood pressure start to rise to compensate. Along with excessive sweating, cardiovascular stress, and the inability to cool (unless you run out of the room!), you are putting yourself in a real and risky situation. Yes you can lose weight but you better replace it and fast when the class is over…. Loss of water is responsible for the immediate decrease in weight. (You could just buy a rubber suit and sit out in the sun on a hot day… overheating and losing a lot of water as your body desperately tries to bring your core temperature down so you don’t die!) Yes you will get the benefits of the exercise but I suggest you skip the high heat and enjoy the benefits of YOGA for weight loss which can often come from the stress reduction practice, breath work, mindfulness and the challenge of the asanas. Always stay hydrated, work hard if you are ready, and listen to your body. Get healthy and fit with less risk and skip the “rubber suit”.
When you sweat you will temporarily lose weight—but this weight is just water weight (water and electrolytes) and not fat weight, and you will put it straight back on as your body is re-hydrated. In addition, as little as a 2% loss of body mass from fluid loss will impair exercise performance. This means a 150-pound student who loses roughly 3 pounds during a heated yoga class from excessive sweating can experience increased heart rate and decreased blood volume, causing a loss of strength and endurance.
Sweat is first and foremost your body’s thermoregulation unit, a means to cool the body down. It essentially will only “cleanse” your skin much in the way a sauna would. “Less than 1% of toxins are lost through sweat” says Dr. Donald Smith, Professor of Environmental toxicology at UC Santa Cruz. Dr. Dee Anna Glaser, professor of dermatology at St. Louis University, and founding member of the International Hyperhidrosis (excessive sweating as a medical condition) Society agrees, “Sweating for the sake of sweating has no benefits and will only release trace amounts of toxins.”