Sweating does not cause weight loss.

FACT: 

Sweating does not cause weight loss; any immediate drop in weight after a workout is due to temporary water loss, which is regained upon rehydration. Experts suggest focusing on a calorie-controlled diet and regular exercise to achieve true and sustainable weight loss, rather than trying to sweat excessively.

Sweating during a workout often feels like proof of a good session –  the more you sweat, the more fat you burn, right? But a recent viral Instagram reel by dietician Bhawesh Gupta has challenged this popular belief.

Gupta appears in the reel asking viewers, “Does more sweating mean more weight loss?” The post, shared in an explanatory and myth-busting tone, has quickly gained traction, amassing over 3.29 lakh views.

In the video, Gupta addresses a common gym habit: people turning off the fan or AC while exercising, assuming it will make them lose more weight. “You must have seen a lot of people turn off the AC and fan while exercising, thinking that the more they sweat, the more weight loss they will have,” he says.

He explains that sweating is simply the body’s natural cooling mechanism. “When our body temperature rises during exercise, it releases water and electrolytes through the sweat glands in the skin, which we call ‘sweat’. This sweat evaporates using body heat, cooling the body and maintaining its core temperature,” Gupta explains.

During activities like weight training, running, or any form of exercise, the body naturally releases fluids (water and electrolytes) through sweat. This fluid loss, Gupta points out, can make the weighing scale show a temporary drop in body weight. However, he clarifies that this change is not real fat loss. “The weight you lose right after a workout is temporary water weight loss,” he explains. “Once you rehydrate and eat your meal, your body regains that weight. That’s why there’s no connection between sweating and fat loss.”

Gupta stresses that true weight loss occurs only when the body is in a calorie deficit, that is, when you burn more calories than you consume. He also warns that excessive sweating can be harmful. “Turn on the AC and fan during workouts so that your body’s core temperature remains stable and sweating is minimal. Too much sweating increases the risk of dehydration, electrolyte imbalance, and muscle cramps,” he advises.

Given the viral reach of this reel and the widespread fitness myth it addresses, First Check examined the science behind whether sweating really causes weight loss.

Does sweating really cause weight loss?

Sweating is often perceived as a sign of a hard workout or proof that fat is being burned, but scientific evidence shows otherwise. Sweating is the body’s natural cooling mechanism: the body releases water and electrolytes through sweat glands, which evaporate to regulate core temperature. Any immediate drop in weight after a sweaty session is primarily due to water loss, not fat, and is quickly regained upon rehydration. True weight loss occurs only when the body is in a calorie deficit — when calories burned exceed calories consumed.

Research has examined this phenomenon for decades. In a 1969 study, the relation between the rate of sweat production and the rate of weight loss was examined under conditions in which the rate of evaporation was small.  The study noted that “the rate of sweat production could be found from the rate of weight loss provided that a film of liquid was maintained over the skin surface. This could be achieved initially by immersing the subject in water containing detergent. Thereafter the film was maintained so long as the rate of weight loss exceeded about 10 grams per minute.”

It also explained that “when the rate of weight loss was changing and the rate of evaporation was constant, the rate of sweat production could be calculated as the rate of weight loss plus 2.5 times the rate of evaporation.”

The researchers added that “when the subject was constantly sprayed with water while being weighed, the correction for evaporation became negligible. In this case there was no lower limit to the sweat rate which could be measured, but spraying considerably reduced the accuracy of the measurement.” This indicates that accurate measurement of sweat requires controlling of external factors and that sweat alone is not a reliable indicator of fat loss.

Practical observations support these findings. For example, some people believe that sweat-heavy workouts like Bikram yoga can help you burn up to 1,000 calories per hour, but this is likely exaggerated. A study shows that during a 90-minute Bikram yoga session, women burned about 330 calories on average, while men burned around 460 calories, which is roughly the same as walking briskly at 3.5 miles per hour for the same duration.

Calories are also burned during activities that do not cause much sweating. For instance, swimming, lifting light weights, or exercising in cold weather still help burn calories.

However, sweating can indicate how intensely you are working during certain exercises. According to the American College of Sports Medicine, healthy adults should aim for 30 minutes of moderate-intensity exercise, enough to break a sweat while still being able to talk, at least five days a week.

In line with these findings, experts agree that sweating alone does not lead to fat loss. Anjali Gupta, Dietician at Dr Ram Manohar Lohia Hospital, explained that “sweating is just a mechanism to balance electrolytes and maintain the body’s cooling system. It is not something that will lead to weight loss; only a calorie-controlled diet or regular exercise can do that.”

She added that “the weight loss seen immediately after a workout is temporary. The drop on the weighing scale is due to water loss, which returns once you rehydrate and eat. Fluids can come not only from drinks but also from foods like fruits and vegetables, such as cucumber or papaya, which have high water content.”

“Excessive sweating can be harmful. Turning off the AC or fan to sweat more can cause dehydration, electrolyte imbalance, and muscle cramps. The water lost during sweating comes from the body’s overall water content, which makes up a major part of blood, muscles, and organs. Losing too much water can affect overall health,” the dietician cautioned.

Elaborating on the role of energy balance, she explained that actual weight loss occurs when there is a calorie deficit, meaning calories burned exceed calories consumed. She added that maintaining energy balance is crucial – consuming more calories than burned results in a positive energy balance, while burning more calories than consumed creates a negative balance, which is necessary for fat loss.

“The effective way to lose weight is through a balanced diet. Fad diets or extreme liquid diets may reduce weight temporarily but can lead to malnutrition, mineral deficiencies, and calcium loss from bones. True weight loss should be gradual and sustainable, ” she advised.

She also highlighted the broader benefits of exercise, “Exercise is not just for weight loss. It helps maintain organ function, body elasticity, and joint health, especially in areas like the hips and knees. Balance is the key – a combination of a healthy diet and regular physical activity is the right approach.”