What makes you sweat even more than you usually do? Exercising in hot weather or a warm room will do it! Exercising in the heat increases your core body temperature faster and you become fatigued faster when the ambient temperature is high. Exercising in the heat doesn’t improve your exercise performance either, as you’re more likely to fatigue and cut your workout short.
With the way your body works hard to maintain normal body temperature when you exercise in hot weather, you might wonder if hot and sweaty exercise sessions burn more calories and whether it gives you a fat loss advantage. What does science say about this?
How Heat Affects a Workout
Other than your core body temperature rising faster, you might wonder what other ways heat impacts a workout. Research shows that exercising in the heat changes the ratio of fuel your body uses.
During a typical workout, your body burns both carbohydrates and fat as fuel. How much of each it uses depends on the intensity of your exercise session. If you work out at a moderate pace where you can talk in complete sentences, your body burns a higher ratio of fat to carbohydrates. But if you pick up the intensity of your training session, your body burns more carbohydrates, in the form of glycogen, and the ratio of fat to carbohydrate fuel usage drops, as your muscle cells use more carbohydrates as fuel.
When you work out in hot weather, regardless of the intensity, your body prefers to use carbohydrates as fuel and, to a lesser degree, fat. In fact, a 2010 study found that working out at 104 degrees F. (a pretty hot temperature) reduced fat oxidation and increased glucose oxidation relative to working out at 68 degrees F. This simply means your body likes to use glycogen or glucose as fuel over fat when you exercise in a hot environment.
Since your body shifts its fuel usage toward carbohydrates in the heat, your carbohydrate requirements go up too, as does your need to hydrate. So, keep a sports drink by your side. A sports drink will supply carbohydrates, water for hydration, and electrolytes to replace the ones you lose through the sweating more.
What about Fat Loss?
Since your body preferentially burns carbohydrates over fat during exercise in hot weather, that doesn’t bode well for fat loss. There’s another reason working out in the heat isn’t ideal for losing body fat. You’ll overheat faster in a hot environment and that may limit the intensity and duration of your workout. Exercising outdoors on a hot day feels less comfortable, and it can affect your mood and motivation. In turn, that impacts performance. A rising core body temperature increases central fatigue so your brain tells you to slow down or stop. Your brain wants to protect you from overheating, and it does so by reducing your motivation and drive. Simply put, you’ll poop out faster!
When you look at the big picture, exercising in a hot environment probably won’t give you a fat loss advantage since you burn more carbohydrates than fat during exercise in hot weather, and the heat can reduce motivation and drive to exercise.
Are There Advantages to Exercising in the Heat?
If you spend lots of time outdoors in the summer, working out in a hot environment helps your body become heat acclimated so you feel more comfortable moving around in the heat. That comes in handy if you do a lot of hiking or play outdoor sports in the summer.
How does your body acclimate to heat? When you exercise in a warm environment, your body adapts by increasing how soon and how profusely you sweat, your blood volume rises, and you become more efficient at controlling your body temperature. When you sweat, you also lose less sodium as your body becomes heat acclimated. Plus, your heart adapts to exercising in warm weather. It takes about two weeks of exercising in the heat for these adaptations to occur.
When you first start working out in a warm environment, you may be susceptible to heat-related muscle cramps. They usually occur in response to excessive loss of sodium through sweating. As your body becomes heat acclimated and you lose less sodium when you sweat, you’re at lower risk of muscle cramps. A way to prevent muscle cramps is to drink an electrolyte-rich beverage to replace sodium and other electrolytes you lose when you sweat.
Risks of Exercising in a Hot Environment
Exercising in the heat isn’t always safe, especially if you’re not heat acclimated. That’s why it’s not a good idea to do it unless you’ve been training for a while and are heat adapted. The risk of overheating is even greater and exercise is more uncomfortable if it’s also humid.
Be aware that certain medications make it harder for your body to release heat. For example, the antihistamines some people take for allergies can impair your body’s ability to cool down. Other medications that may interfere with temperature regulation include calcium channel blockers, beta-blockers, antipsychotics, and stimulant medications. Talk to your physician about whether you’re taking medications that make it easier for you to overheat.
If you must work out in a hot environment, dress as lightly as possible to allow your body to safely sweat and release heat. Listen to your body too. If you feel lightheaded, dizzy, nauseous, or have blurred vision, stop your workout and rehydrate with an electrolyte-rich beverage. Follow the guidelines for staying hydrated during a workout too. You’ll lose fluids and electrolytes much faster when it’s hot outside.
The Bottom Line
Exercising in a hot environment doesn’t offer a significant fat loss advantage, but it can help you get heat acclimated. That’s useful if you’ll be going on a long hike in hot weather or you play outdoor sports in the heat. If you exercise in the heat, do it safely!
- Nybo L, Rasmussen P, Sawka MN. Performance in the heat-physiological factors of importance for hyperthermia-induced fatigue. Compr Physiol. 2014 Apr;4(2):657-89.
- Sports Med. Jan-Feb 1985;2(1):8-20. doi: 10.2165/00007256-198502010-00002.
- Health ENews. “Some widely used medications may put you at risk for heat stroke”
- Gatorade Sport Science Institute. “Heat Acclimatization to Improve Athletic Performance in Warm-Hot Environments”