An infrared sauna uses specialized heaters that emit invisible infrared radiation. Unlike traditional saunas, which heat the air, infrared light directly penetrates the body and gently elevates its core temperature. This radiant heat delivery is effective at lower air temperatures, typically between 100°F and 130°F, compared to the 180°F to 220°F seen in conventional models. Many users are interested in whether this process contributes to weight loss and calorie burning.
The Body’s Thermoregulatory Response
Sitting in an infrared sauna triggers an energy-intensive physiological response as the body works to maintain its internal temperature, a process known as thermoregulation. The infrared heat raises the core body temperature, prompting the body to initiate immediate cooling action. This cooling effort is the mechanism responsible for increased caloric expenditure during a session.
To dissipate the excess heat, the heart pumps blood faster, increasing circulation to the skin where heat is released through sweat. This elevated heart rate and increased cardiovascular workload effectively mimic the effects of low-level physical activity. The body’s basal metabolic rate increases as it expends energy to power this internal cooling system, driving vasodilation and sweat production. The energy cost is a direct result of the body’s effort to restore homeostasis in the face of external heat stress. This metabolic boost is comparable to the energy used during a brisk walk or light exercise, even though the individual is sitting still.
Quantifying Caloric Expenditure
The precise number of calories burned is highly variable and depends on individual factors like body mass, metabolic rate, duration, and session temperature. Scientific estimates indicate a modest, measurable increase in energy expenditure above the Resting Metabolic Rate (RMR). Studies suggest that a typical 30-minute session may burn an additional 100 to 200 calories, which is similar to the energy consumed during a light-effort activity.
Other estimates suggest 400 to 600 calories per hour, but these figures are often based on traditional saunas or extrapolation models. A study involving multiple 10-minute sessions found participants burned between 73 and 134 calories per segment. This calorie burn is a sustained effort, but it does not replace the energy expenditure of more vigorous exercise. While a sauna session contributes positively to overall energy balance, it should be viewed as a supplementary tool rather than a primary method for achieving significant weight loss.
Differentiating Water Loss from Fat Loss
The most immediate effect of an infrared sauna session is the temporary weight reduction observed afterward. This change is almost entirely attributable to the loss of body fluid through profuse sweating, which can lead to a loss of up to one liter of water during a typical session. This fluid loss represents water and electrolytes, not metabolized fat.
Fat loss, or the burning of calories stored in adipose tissue, occurs when the body maintains a calorie deficit over time. The weight lost from sweating is rapidly regained once the individual rehydrates, which is necessary for health and safety following heat exposure. It is a misconception to equate this temporary weight drop with actual fat loss. The true value of the sauna lies in the metabolic increase and potential benefits for stress reduction and muscle recovery, which indirectly support a healthy lifestyle.