No, sweating does not burn fat. In fact, sweat (perspiration) might not even be an indication that you are burning extra calories! We sweat during a tough workout because our muscles are generating too much body heat to disperse by normal circulation. The sweat droplets that form on your skin whilst exercising have no body fat dissolved in them. Here’s why:
The average person has about 200 sweat glands opening onto the surface of ever square centimetre of skin covering their body. That makes for between 2 and 4 million sweat glands per person. There are two main types of sweat glands. One makes the oily type of sweat (think everyday armpits), and the other makes the watery type. Even though these glands are surrounded by fat cells, they do not function by drawing fat out in any way. Instead, sweat is taken from body fluids found in between cells (extracellular fluid).
Purpose of Sweat
Sweat is excreted for many different reasons, but the type we are talking about here is specifically made for cooling purposes. It is mostly water, which spreads out on the skin surface and evaporates into the air. In so doing, it cools the body down in the same way that a water-soaked T-shirt does on a hot day. Fat stores would be useless for this purpose because fat does not evaporate easily!
Saunas don’t burn Fat
Think about it, if sweating really did burn fat, then saunas would be way more popular than they are right now. So would habanero chilli peppers, night sweats, and hot flushes. The average adult can perspire 12 litres of sweat in a day, so imagine the weight loss possibilities if, say, 10% of that was body fat! Sweating does cause temporary weight loss (water weight), but it does nothing special to burn fat.
Cold Workouts are Effective
Whilst exercising in cold temperatures can be associated with elevated injury risk, it is just as effective (if not more so) at burning calories than other workouts. Climbing Mt. Everest in a blizzard will cause much less sweat than running on a hot Gold Coast beach, but both workouts will burn calories effectively. Sweating during a workout is a sign of a hot body, but it is not necessarily an indication of fat burn.
Some People just Sweat More
There is a truly massive difference in the number of sweat glands each person has. Some people have twice as many sweat glands as others, thus they tend to sweat almost twice as much. If sweating really caused fat burn, then sweaty people would have a huge advantage in the weight loss department. Think about all the heavy sweaters you know – are they generally skinny?
The Surprise Twist
So, we’ve just written a page explaining that sweat does not cause fat burn, but here’s the twist: sweat can have “pieces” of “used up” body fat in it! Perspiration, along with urination and defecation, is one of the body’s excretion mechanisms. Excretion is the process of removing unwanted and excess products from the body. Fat metabolism produces water, some of which ends up being evaporated away as sweat. There may in fact be burned fat in your gym headband!