Weight loss due to hot yoga depends on many factors, including the type of class. For example, Bikram and Baptiste power yoga are both challenging, heart-pumping forms of yoga that are intensified by heat. But other types, such as yin or restorative yoga, don't increase your heart rate enough to result in fat loss, even in a heated room. Sweating is a huge part of hot yoga, but a lot of what you're shedding is water weight, which you'll "gain back" once you rehydrate - something that is critical after a class.