Sweat may be an indication of an intense, fat-burning workout, or it could simply be a reaction to an especially hot or humid day. Sweating doesn't burn fat; it helps regulate your body temperature. If high-intensity exercise causes you to sweat, you may be burning significant calories -- many of which may come from fat. But, forcing yourself to sweat more by working in hot conditions or wearing heavy clothes won't lead to additional fat loss.
What Is Sweat?
Sweat is your body's reaction when your core temperature exceeds 98.6 degrees Fahrenheit. In an effort to maintain your body's preferred temperature, your brain activates the sweat glands in your skin. You start to lose water along with salts, sugar and minute amounts of the waste products created during protein breakdown. Between 2 million and 4 million sweat glands on your body release sweat to cool you down. Some people sweat more than others, even in the same conditions. The temperature and humidity level does influence your sweat rate, but so does your genetics, gender, age and fitness level.
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When moisture in sweat evaporates off your skin, it cools you down. You sweat more in heat and humidity, but that doesn't mean you're burning more calories or fat; it simply means your body has to release perspiration to bring your body temperature down. Larger people tend to sweat more because they have a greater amount of body mass to cool down. Fitter people also tend to sweat more, but this is because their cooling system is especially efficient -- giving them the ability to work harder for longer.
How You Burn Fat
Fat doesn't technically burn or melt. It gets released from fat cells to provide your body with energy. Your body breaks down the fat into its parts -- fatty acids and glycerol -- which are then metabolized. The more energy you need, the more your body pulls from your fat cells. The bodily function that causes you to use fat for energy operates independently of the one that causes you to sweat.
Purposefully exercising in a hot or humid environment doesn't mean you're working harder to burn more fat. You're simply raising your body temperature to a point that prompts you to sweat more. Working hard in a hot, humid conditions can actually be dangerous. Wearing sweats or other warm clothing may also prompt you to sweat more, but it won't make you lose fat faster than someone in shorts. It'll simply make you sweat sooner and possibly lose more water weight, not fat.
The Relationship Between a Sweaty Workout and Fat Burn
Sweat doesn't burn more fat, but it can be an indication that you're working hard. The more intensely you work, the higher your core temperature rises, which results in perspiration to cool you down. If your sweat is a result of a hard workout -- and not the external temperature -- you're likely using energy and burning fat.
Sitting on a beach on a 100-degree day doesn't require a lot of energy and doesn't use notable amounts of fat. You sweat because you're just in need of serious thermoregulation. When you work hard in frigid temperatures, such as running a winter marathon, you still burn fat even if your body doesn't sweat as much to cool you down.
Workouts that don't prompt you to sweat a lot are still beneficial, too. Yoga, pilates and stretching hone your balance, flexibility and core strength but may not make you drip with sweat. You're still building a stronger, more functional body.
Sweat and Weight Loss
You may notice that after a shirt-drenching workout, the number on the scale has gone down. You haven't dropped a few pounds of fat, but you have lost a fair amount of fluids. You should replace that lost weight with water or a sports drink to avoid dehydration.
If you enter a workout dehydrated, you may not sweat efficiently either. Your body increases in temperature, but you're unable to effectively cool the body back down. This results in a decreased ability to perform and is why hydration is critical to exercise success.
The American Council on Exercise recommends you consume about 20 ounces of water two to three hours before you begin a big workout; 8 ounces just before you exercise; 8 ounces every 20 minutes during exercise and another 8 ounces within 30 minutes of completing the session. Weigh yourself before and after the workout, too. When the scale says you've lost notable weight immediately after a workout, drink 16 to 24 ounces of water to replace each pound you've lost.