According to the Centers for Disease Control, nearly 75 percent of the American adult population is overweight or obese (1). That means a large proportion of people are currently dieting and exercising to lose weight.
And it’s not just overweight people that train and watch what they eat to lose weight; fit and healthy people do too. After all, there is a big difference in appearance between 15-20 percent body fat and getting your body fat levels to under ten percent. If you want lots of muscle definition, you need to be lean.
There are lots of workouts you can do to shed that unwanted weight, from HIIT to circuit training to bodybuilding to good old steady-state cardio.
But does sweating affect how much weight you’ll lose? In this article, we reveal the truth about sweating and weight loss.
Body Composition 101
When you hop on the scales and weigh yourself, the reading tells you your total body mass. However, your body mass is made up of several different components:
- Muscle weight
- Bone weight
- Organ weight
- Fat weight
- Glycogen stores
- Undigested food
- Stored minerals
- Water and other fluids
While reducing any of these components will lower your scale weight, it’s fat that you really want to lose if you want to be leaner and healthier.
Body composition is usually expressed as a body fat percentage. For example, if your BF% is 17%, that means 17% of your body weight is fat, and the rest is designated as lean tissue – which is basically everything else.
To burn fat and lower your BF%, you need to reduce your calorie intake and increase your energy expenditure. This creates a calorie deficit, and your body will use fat for fuel to make up this energy shortfall. You CAN lose fat with diet or exercise alone, but it’s generally accepted that combining these two approaches works best.
Sweating also leads to weight loss but won’t necessarily affect your body fat percentage.
Sweat loss vs. Fat loss
Exercise usually leads to sweating. You’ll sweat more if you work out in a warm environment or wear something like a plastic sauna suit. Some people are genetically programmed to sweat more.
However, sweat loss and fat loss are two very different things.
Your body produces sweat through perspiration to stop you from overheating. It releases water which evaporates from your skin, taking heat with it. If you sweat heavily while you exercise, you will probably weigh less at the end of your workout.
For example, if you sweat out a pint of water and do not rehydrate during or immediately afterward when you hop on the scales, you will have lost about half a pound. One liter of water (about 2.11 pints) weighs one kilogram or roughly 2.2 pounds.
Unfortunately, while you’ll weigh less, this weight loss is temporary. As soon as you drink any water, you’ll replace those lost fluids, and your weight will increase again.
While your workout will have burned calories and can contribute to fat loss, you probably won’t be able to measure that effect on the scales, as even a very intense workout burns a relatively small amount of fat.
It’s estimated that a pound of body fat contains roughly 3,500 calories. Most people should be able to burn 500-600 calories per hour of exercise. That equates to about 2¼ ounces of fat. That’s a very small amount compared to how much water you can lose (and regain) through sweating.
So, while sweating does lead to weight loss, it’s probably not the type of weight you want to lose. Also, whatever weight you have lost will be regained the moment you rehydrate.
The Downside of Trying to Sweat Off Weight
While there is nothing wrong with getting hot and sweaty during your workout, it’s mostly a bad idea to try and sweat off weight. At best, weight lost through sweating is temporary and quickly regained.
Ideally, you should drink during and after your workout to replace lost sweat. That way, your body weight will remain largely unchanged. As well as being an ineffective way to lose weight, other reasons that trying to sweat yourself slimmer is a bad idea include:
As your core temperature rises and you sweat more, your body takes water from various sources, including your blood plasma. As you lose water from your blood, it starts to thicken, and your heart has to work harder to pump it around your body (2).
This causes your heart rate to increase or drift, even if your workout intensity remains unchanged. However, with your heart working harder than usual, you’ll probably start to feel tired and may even need to bring your workout to a premature end.
The best way to minimize cardiac drift and prolong your workout is to consume plenty of hydrating fluids while you train.
You don’t just lose water when you sweat. Sweat also contains a suspension of minerals called electrolytes. The main electrolytic minerals are:
Low levels of these minerals can lead to impaired muscle contractions, cramps, and heartbeat irregularities. While you could chew a few multimineral tablets to restock your electrolytes during exercise, it’ll be a whole lot easier if you consume them along with a hydrating drink. That’s why most sports drinks contain electrolytes.
Lower workout performance/duration
Your workout will suffer if you sweat a lot and don’t replace the lost fluids and minerals. If workout intensity falls or you have to cut it short because of dehydration or overheating, you won’t burn as many calories, making your training less effective for fat loss.
Sweating is your body’s response to being too hot. If you sweat heavily but don’t rehydrate during your workout, you risk developing exercise-induced hyperthermia (3).
Hyperthermia means that your core temperature becomes dangerously high. Overheating will lower your workout output, bring your session to a premature end, and can also result in severe illness and even death.
Sweating is a natural part of the workout experience. As your body heats up, it produces sweat to stop you from overheating. The hotter you get, the more you sweat. It would be a terrible idea to try and artificially stop your body from sweating!
While sweating is mainly unavoidable, some people find it uncomfortable, and if you’re trying to “sweat off weight,” you may find the entire exercising process too unenjoyable to continue.
When Sweating Off Weight Can Be Helpful
While trying to sweat off weight is usually pointless, there are situations when it may be helpful or even necessary.
Imagine you are a weightlifter who competes in the 90kg category. When it’s time to weigh in before your next meet, you step on the scales and discover you weigh 92kg – two kilos/4.5 pounds overweight.
You could step up a weight category, but that means competing against lifters that are heavier and stronger than you. Instead, you wrap yourself in plastic bin bags, hop on a stationary bike, and sweat off those extra pounds so that, when you weigh in again, you’re back under the 90kg weight limit. This is called making or cutting weight.
Once you’ve successfully passed the weigh-in, you can replenish those lost fluids and compete in your original weight category.
Is this cheating? Kind of, but it’s also a very common practice. In most sports, it’s usually best to be at the top of your weight category and not at the bottom, and temporarily losing water weight means that athletes can compete at a lower weight category and against smaller opponents.
Athletes from sports with weight categories use sweating and dehydration to temporarily lose weight, including:
- Olympic weightlifting
However, the caveat is that these athletes rehydrate as soon as possible to ensure that they are able to perform at their best. This may even involve intravenous fluid replacement to speed up rehydration.
Unfortunately, making weight sometimes goes wrong, and some athletes are unable to replace all the fluids they’ve lost, which hurts their performance. That’s especially true if you need to lose a lot of weight. Some dehydrating practices are also dangerous, such as the use of diuretics or working out in a sauna (4). Athletes have died cutting weight.
So, while sweating CAN help you lose weight, it’s a myth that it helps you lose fat. Sweat off a pint of perspiration, and you’ll weigh about a pound less. But, as soon as you rehydrate, you’ll be right back where you were.
That said, sweating during your workout is a good indicator you are working hard enough to burn plenty of calories, so it’s not a bad thing to perspire during exercise. However, to avoid the drawbacks of dehydration, such as a shorter or less intense workout, it’s best to consume fluids during and after your workout. That way, you’ll be able to maximize fat loss.
Fighters and other athletes cut weight by sweating, but only to compete in a lower weight category. Unless you are about to weigh in for an MMA bout, losing weight through sweating is largely pointless and won’t do anything for your body fat percentage.
Instead of trying to sweat off your excess weight, eat a little less and exercise a little more. That’s the most effective way to burn fat and get leaner.
1. CDC: Obesity and Overweight https://www.cdc.gov/nchs/fastats/obesity-overweight.htm
2. PubMed: Fluid Replacement and Glucose Infusion During Exercise Prevent Cardiovascular Drift https://pubmed.ncbi.nlm.nih.gov/1757323/
3. PubMed: Hyperthermia During Exercise – A Double-Edged Sword https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5198803/
4. PubMed: The Current State of Weight-Cutting in Combat Sports https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6572325/