Benefits Of Sweating For Weight Loss

Overview

For decades, many of us have been led to believe that, unless we are soaked to the bone and drowning in a puddle of sweat, our workouts do not ‘count’ and our scale weight will never budge. How much of this is fact and how much is a myth? Does  our weight loss success depend  on how much sweat we produce? Should we be forcing ourselves to sweat more to  burn more calories and fat? 

Eager to have these and many more intriguing questions answered? Do not ‘’sweat’’ it! You have come to the right place! 

Why do we sweat?

Sweating is a vital and highly efficient biological mechanism that functions to regulate body temperature (thermoregulation) during periods of extreme heat and/or strenuous physical activity.¹ In humans, sweat is excreted mainly from the eccrine sweat glands and onto the skin surface, where it evaporates, thus working to effectively cool the body down. Sweat contains an aqueous mixture of both water and salt (NaCl or sodium chloride) as well as ions and electrolytes such as sodium, calcium, chloride, and potassium.

Do you lose weight from sweating?

In a nutshell, no. Although sweating can result in rapid weight loss, the weight that is lost is primarily in the form of ‘’water weight’’,² meaning that it is only temporary, and will be immediately regained following fluid consumption. If one wishes to lose weight safely and effectively, fat loss, rather than water weight loss, should be the aim. Interestingly, research suggests that when we lose fat, a very large proportion is expelled from the body in the form of carbon dioxide (CO₂), and only a tiny fraction is released in bodily fluids including sweat, urine, breath, tears, and faeces.³ In fact, if one loses 10kg of fat, 84% (8.4 kg) is exhaled out of the lungs and only 16% (1.6 kg) is excreted as water, of which a minuscule amount is in the form of sweat. From these numbers alone, it is evident that very little, if any, weight is lost in the form of fat via sweat, suggesting that sweat does not burn fat or facilitate fat loss. Rather, eating fewer calories⁴ and/or performing regular exercise does. 

How many calories does sweating burn?

In simple terms, we burn calories⁴ by expending more energy (out) than we consume (in). Energy expenditure can be increased by engaging in more physical activity, which as discussed above, can trigger the sweating (perspiration) process. Therefore, it is the exercise itself, rather than the sweating, that contributes to calorie burn and eventually, weight loss. Sweating merely serves to cool the body down during exercise.¹

The amount of calories we burn during exercise⁴ depends on multiple factors including the exercise type, intensity, and length as well as age, sex, body size, and body composition. It is a common myth that sweating more equates to a higher calorie burn, leading many to believe that very sweaty workouts such as Bikram yoga⁵ (or ‘’hot’’ yoga) can burn as many as 1000 calories in 90 minutes! However, this myth was debunked by a study that showed that men and women burnt 460 and 330 calories, respectively, during Bikram yoga.⁵ Although producing a significantly higher amount of sweat, the number of calories burnt was reported to be no different from walking briskly at a moderate pace (3.5 miles an hour) for 90 minutes. The findings of this study highlight one critical point: sweating little to none during a workout does not correlate to less calorie burn and thus, less weight loss. Indeed, according to Harvard Health Publishing,⁶ exercises that do not turn you into a sweat-fest such as light walking, light yoga, pilates, strength training, and swimming can still help you burn a good amount of calories and lose weight. 

Why do some people sweat more than others?

There are many factors, of which we have no control, that influence how much sweat we excrete including age and sex, with younger adults and men reported to excrete more sweat than older adults and women, respectively.¹ Sweat quantity and rate are  also determined by the number of sweat glands we were born with, our health, fitness, hydration, and heat acclimation (or heat tolerance/adaptation) statuses, as well as our weight and sleep (to name a few).⁷

People that have a higher weight tend to sweat more compared to leaner individuals.⁷ Understandably, this is because more sweat is needed to cool a body with a larger surface area and body mass. Additionally, fit people  have been demonstrated to sweat more compared to those that are unfit.⁸ Although seemingly paradoxical, by sweating more and thus, being more efficient at ridding the body of excess body heat, fitter people can  push themselves harder and last longer during strenuous activities compared to less fit individuals.⁹ 

What are the benefits of sweat?

Despite having no established beneficial effect for weight loss (at least, to date) and functioning mainly to regulate core temperature, sweating has multiple health benefits including the following:¹⁰,¹¹, ¹²

1. Protects against disease: Sweating helps eliminate excess metabolic and dietary waste products as well as toxins
2. Improves skin health: Sweating maintains skin hydration, acting as ‘’the most efficient natural moisturizer’’, as quoted by researchers in a 2018 study
3. Prevents bacteria from entering the body: Sweat contains glycoproteins (proteins with a carbohydrate-based glycan group attached) that bind to bacteria and ‘’wash’’ them away from epithelial surfaces within the body, hence preventing their entry

How effective is sweating for losing weight?

As evidenced by the myriad scientific articles presented in this article so far, sweating is not an effective tool for weight loss or calorie burn. However, sweat can help one gauge their perceived exertion level,¹³ or, simply put, the effort and intensity they have put into a workout. This can be helpful to ascertain whether one is on the right track towards weight loss if that is the goal. 

Regardless, aiming or forcing your body to sweat more in hopes of burning more calories and hence, losing more weight is not a wise or sustainable thing to do. Days before competing, wrestlers and horse jockeys ‘’sweat out’’ water weight rapidly by restricting their fluid intake, engaging in sauna bathing, and wearing a sauna suit or sweat suit whilst performing vigorous exercise.¹⁴ Unsurprisingly, due to profuse sweating, many end up with cases of severe dehydration, as reported by studies.¹⁴  Severe dehydration is a dangerous health risk that could result in death. That is why people with hyperhidrosis, a health condition characterised by excessive sweating, should be very wary of their fluid intake, making sure to rehydrate regularly especially in hot climates and during strenuous exercise.¹⁰

Summary

The primary function of sweat is to regulate the human body's  core temperature. Contrary to popular belief, sweating offers no benefits for weight loss and is not a good indicator of calorie burn, exercise performance, and effectiveness, or even one’s fitness level. Sweating may result in rapid weight loss, making it tempting for many to bathe in saunas and wear sauna suits or sweat suits. However, the weight lost from sweat is not permanent as it results in water weight loss and not fat loss. Such a small fraction of fat is lost in sweat when we lose weight that it is negligible. The majority of fat is lost in the air as CO₂. 

Instead of focusing on how much sweat is excreted during each workout, one should consider looking at more effective measures for exercise performance and calorie burn including both heart rate and breathing rate as well as muscle fatigue.¹³ Aiming to achieve weight loss via excessive sweating is not recommended as it can result in severe dehydration, and eventually, death, if untreated. Instead, for healthy, sustainable, and permanent weight loss, one should aim to lose weight gradually by adopting a healthy lifestyle that combines both regular physical activity and a healthy, balanced, low-calorie diet.