Let me introduce you to your good friend, sweat. Ignore the gross feel and the potential for B.O. for the moment, and think about what it does for you: When your body gets too hot, threatening to raise your core temperature over what’s healthy, little glands in your skin squeeze drops of moisture onto its surface. As soon as a breeze hits those droplets, they evaporate, taking some of your body heat away with them.
Pretty cool, huh? So let’s look at what it means to sweat while you’re working out:
- You are hot
- Your body wants to cool you down
- That is it. I promise.
Seems too simple? Let’s look at the scenarios where you sweat. On a hot day, while you’re lounging around? Check. Indoors in the air conditioning, when you’re doing a workout? Also check. Exercise raises your body temperature (muscles generate heat as they work), so you’ll feel warm and you’ll start to sweat. It’s not the exercise itself that makes you sweat, it’s the heat.
You can get a great workout even if you don’t sweat very much
At the same ambient temperature, a harder workout might result in more body heat, so we’ve built up an association between sweating and working hard. It’s deceptive, though.
If you go for a 16 km run in the heat, you’ll sweat buckets. 16 km on a treadmill at room temperature, and you may not sweat quite as much, but you’ll still be dripping. Go and run 16 km in the winter, though, and you’ll barely be damp. That’s because your body doesn’t have to worry about cooling itself down.
Why do some people sweat more than others?
One of biggest differences between people who sweat a lot and those who sweat less is body size. It doesn’t matter whether you’re fat, muscular, tall, or some combination thereof; the more of you there is, the harder your skin has to work to cool you down, and thus the more you sweat. When compared to average-sized or larger adults, children and petite folks have more surface area (skin) compared to the amount of body mass that needs cooling. In other words, they have a higher surface-area-to-volume ratio, so they can cool down with less sweat. It’s just physics.
If you lose a substantial amount of weight, you may end up sweating (slightly) less for this reason. On the flip side, the fitter you are, the more you might sweat, as research suggests runners’ bodies turn on the sweat glands sooner than sedentary people, and that they sweat more during the same workout.
Finally, if you feel like you’re the biggest sweater in your friend group, look at whether you’re actually doing appropriate comparisons. If you’re dripping when you run in the noonday sun and you see your friend post a selfie from the air-conditioned gym, you shouldn’t expect the two of you to sweat the same amount.
What’s the connection between sweat and weight loss?
Sweating a lot during a workout does not mean you’re losing fat, so let’s bust that myth right there. Sweating a lot can make you lose water weight, though, which is only temporary.
Our bodies contain a certain amount of water in our blood and in the various cells and compartments we’re made of. We can lose a little bit of it, become slightly dehydrated, and barely notice. Or we can drink a ton of water and become very hydrated, and have to pee a lot to get back to a normal level. In extreme cases, we can get so dehydrated it threatens our health, but that’s rare with normal activities.
When you sweat, and that sweat evaporates or gets rubbed off (you mop your brow with a towel, let’s say), that’s water leaving your body. You can actually weigh yourself before and after a workout and notice a change in weight if you sweat enough. Every pound of weight you lose is two cups of water that has left your body. So technically you “lost weight,” but it wasn’t fat. You’re just due to drink two cups of water, and then you’ll be hydrated and happy again.