Identifying Heat Exhaustion Symptoms While on a Weight Loss Journey

Article Summary:

• If you’re on a weight loss journey, increased physical activity and a reduced-calorie diet can heighten the risk of developing heat exhaustion during hot weather.
• Recognizing the symptoms of heat exhaustion, and quick intervention, can prevent heat exhaustion from developing into heat stroke.
• To stay safe, remember to drink plenty of water, avoid going outside during the hottest part of the day and try making adjustments to your exercise routine.

Identifying Heat Exhaustion Symptoms While on a Weight Loss Journey

Whether you're on a weight loss or weight management journey, or you're simply trying to add more daily movement to your routine, spending time outdoors can be hugely beneficial for your physical and mental health. In fact, recent research has revealed that 36% of Canadians on a weight loss journey plan for an active outdoor summer adventure.

But in hot weather, it's important to take some extra precautions to keep yourself safe and prevent the onset of heat-related illnesses, like heat exhaustion.

In this article we'll explain why those on a weight loss journey need to take proactive steps to prevent heat exhaustion. We'll also share the signs and symptoms of heat illness to watch out for, and tips on how to stay safe during extreme heat.

What is heat exhaustion?

Heat exhaustion happens when your body overheats and its cooling system becomes overwhelmed.

Heat exhaustion is one of the most frequently diagnosed heat-related illnesses in Canada. [1] But although it's a relatively common medical condition, it can be dangerous if left unmanaged.

What causes heat exhaustion?

Think of your body’s cooling system like a built-in thermostat: when your body gets too hot, it responds by increasing sweating and sending more blood to your skin so heat can be released. [2] However, if you lose too much water and salt through heavy sweating, especially in extreme heat, your body may not be able to cool itself properly. This can cause heat exhaustion. [3]

Excessive sweating without enough fluid replacement can also lead to dehydration and salt loss, which can affect normal body function. [4] That’s why vigorous outdoor exercise on a hot day can increase the risk of both heat exhaustion and dehydration.

Are people on a weight loss journey more susceptible to heat exhaustion?

Heat exhaustion may affect some people more than others. For example, pregnant people, young children and those over the age of 45 may need to take extra care during hot weather. [2]

Certain medical conditions, like heart problems and high blood pressure, may also increase your health risks during periods of extreme heat. [5] [2]

But what about if you're on a weight loss or weight management journey? If you're increasing your daily movement, or reducing your calorie intake, you may need to take extra care during hot weather too. This is because heat stress can increase your body's need for carbohydrates, which can make you burn more energy than usual. [6] And, because you may burn calories more quickly in heat, this may cause your stamina to drop and increase the risk of fatigue. This, coupled with increased sweating during hot weather, may also put you at great risk of developing heat exhaustion. [7]

Remember to stay hydrated by drinking plenty of water, eat a balanced and varied diet and avoid exercising in extreme heat. This will help you stay safe and keep your fitness goals on-track during hot weather.

Heat exhaustion vs heat stroke

Heat exhaustion can sometimes be confused for other, similar heat-related illnesses:

Heat stroke: If left untreated, heat exhaustion can quickly develop into heat stroke. Heat stroke occurs when the body's cooling system fails. Our normal core body temperature should average 37℃ (98.6℉). However, if you experience heat stroke your body temperature could raise to 40℃ (104℉). [8] [9]

According to the Canadian Red Cross and Health Canada, the key signs and symptoms of heat stroke are:

• Hot skin
• Severe headache
• Unresponsive
• Seizures
• Altered behaviour (bizarre, irritable, aggressive or confusion)
• Rapid, shallow breathing
• Rapid, irregular, weak pulse
• High body temperature [8] [10]

Heat stroke is a dangerous condition which requires urgent medical attention. If you think someone is experiencing heat stroke, dial 911 immediately.

In contrast, the key signs and symptoms of heat exhaustion are:

• High body temperature
• Sweating
• Headache
• Fatigue
• Confusion
• Diarrhea
• Muscle cramps
• Rapid breathing and heartbeat
• Extreme thirst
• Decreased urination and unusually dark yellow urine
• Nausea or vomiting
• Dizziness or fainting
• Anxiety [2] [8] [10]

If you think you (or someone else) is experiencing heat exhaustion and their symptoms aren’t improving within a few hours (or if they’re showing signs of heat stroke), dial 911 for urgent medical attention. [8]

Two other common heat-related illnesses are:

Heat cramps: Heat cramps are muscle spasms which are often caused by an imbalance between our salt and fluid levels (for example, exercising outdoors during hot weather without proper hydration).

Although heat cramps can be painful, any discomfort should start to subside once you've rehydrated. [2]

Heat rash: A heat rash is a type of skin rash which is caused by plugged sweat glands. The spots are normally small and red, and are often itchy. [2]

Like heat cramps, a heat rash can be self-treated. Move to a cool, shady spot until the rash has subsided.

How to treat heat exhaustion

If you suspect some is experiencing heat exhaustion and is nauseous or vomiting, is dizzy or has fainted or is presenting as anxious, dial 911 for urgent medical assistance.

For any other symptoms of heat exhaustion, immediately move them to a shady spot. Splash cool water on their clothes and remove any unnecessary or heavy layers. [2]

They should also rehydrate. If possible, try to offer an isotonic sports drink or electrolyte-enhanced water. If these aren't available, cool water is best. [2]

The symptoms should improve within an hour, but if they don’t, seek urgent medical attention. [8]

How to prevent heat exhaustion

Hydration

We should always aim to drink 6-8 glasses of fluids daily (water is best). But during spells of hot weather, it's even more important to stay hydrated. Aim for small, frequent sips throughout the day, and try to drink before you feel thirsty to stay on top of your fluid intake. [11]

Prep your home

If a heat wave's on the horizon, make sure you're ready. Keep an eye out for heat warnings from your local media outlets, to help plan your outdoor activity. And if you have an air conditioning unit, it's worth checking that it's in good working order before the hot weather starts.

Take regular breaks from the sun

During periods of extreme heat, it's best to avoid going outside during the hottest part of the day. When you do go outside, be sure to take plenty of regular breaks in cool, shady spots to prevent overheating. And, if you plan on doing outdoor exercise, it might also be worth adjusting your routine to shorter, more gentle exercises during the cooler parts of the day.

Before going outside, be sure to apply an SPF sunscreen (ideally SPF 30+) to protect your skin. Remember to reapply it regularly throughout the day. [2]

Maintaining a sustainable weight loss program can be challenging, especially during hot weather. But with certain adjustments, you'll be able to safely maintain your healthy habits and prevent the risk of heat exhaustion.

And if you're considering weight loss treatment, help is available. Find out which treatment may be suitable for you with MedExpress.

References

1. Canada H. Heat-related morbidity and mortality in Canada - Canada.ca [Internet]. Canada.ca. 2021. Available from: https://www.canada.ca/en/health-canada/services/publications/healthy-living/heat-related-morbidity-mortality.html
2. Government of Canada CC for OH and S. CCOHS: Hot Environments - Health Effects and First Aid [Internet]. www.ccohs.ca. 2023. Available from: https://www.ccohs.ca/oshanswers/phys_agents/heat/heat_health.html
3. Székely M, Carletto L, Garami A. The pathophysiology of heat exposure. Temperature: Multidisciplinary Biomedical Journal [Internet]. 2015 May 27;2(4):452. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4843928/
4. Mayo Clinic. Dehydration - symptoms and causes [Internet]. Mayo Clinic. 2025. Available from: https://www.mayoclinic.org/diseases-conditions/dehydration/symptoms-causes/syc-20354086
5. Canada H. It’s much too hot! Protect yourself from extreme heat - Canada.ca [Internet]. Canada.ca. 2024. Available from: https://www.canada.ca/en/health-canada/services/publications/healthy-living/too-hot-protect-yourself-extreme-heat.html
6. Febbraio MA. Alterations in Energy Metabolism During Exercise and Heat Stress. Sports Medicine [Internet]. 2001;31(1):47–59. Available from: https://link.springer.com/article/10.2165/00007256-200131010-00004
7. Do You Burn More Calories in the Heat? [Internet]. Healthline. 2021. Available from: https://www.healthline.com/health/fitness/do-you-burn-more-calories-in-the-heat#calories
8. https://www.redcross.ca/training-and-certification/first-aid-tips-and-resources/first-aid-tips/summer-safety/heat-stroke-heat-exhaustion
9. Canada H. Communicating the Health Risks of Extreme Heat Events [Internet]. aem. 2011. Available from: https://www.canada.ca/en/health-canada/services/environmental-workplace-health/reports-publications/climate-change-health/communicating-health-risks-extreme-heat-events-toolkit-public-health-emergency-management-officials-health-canada-2011.html
10. Canada H. Fact Sheet: Staying Healthy in the Heat - Canada.ca [Internet]. Canada.ca. 2024. Available from: https://www.canada.ca/en/health-canada/services/publications/healthy-living/fact-sheet-staying-healthy-heat.html
11. Canada GA. Sun and heat safety tips for travellers [Internet]. Travel.gc.ca. 2012. Available from: https://travel.gc.ca/travelling/health-safety/sun-tips