CPR First Aid

Can you Burn More Calories When You Have a Fever?

Can you burn more calories when you have a fever? This is a question that many people in Perth have asked. Especially since your body is working harder to fight off the infection which requires more calories. Let’s see below how it happens and how many additional calories may be burned in a day if someone has a fever.

How Many KJ a Day to Lose Weight?

When trying to lose weight, it is important to pay attention to a person’s KJ or kilojoules. There are two things two take into consideration: the number of kilojoules taken in via eating and the burned kilojoules through exercise. Both of these are important. The recipe is simple but very hard to follow. A person must consume less kilojoules and burn more. 

How Many Kilojoules Should I Burn a Day?

Studies suggest that people need to burn 2,100 kilojoules more than what they consume on a daily basis. It is recommended that a person consumes over 8,000 kilojoules a day. So, either a person burns 10,100 kilojoules through exercise, or the daily consumption can be lowered via diet so that the amount of exercise can also be decreased. 

How many kilojoules per day for a woman? Whether it be a man or woman, the recipe stands. Burn more than what is consumed. Now, apart from exercising, are there other ways to burn more calories? Does being sick help? Let’s find out. 

Do You Burn More Calories When You Are Sick?

When you have a fever, there is an increased metabolism since your body raises its temperature. This is the immune system’s way of trying to beat the bugs. When there is increased metabolism, there is an increase in calories being burned, according to Scientific American.

Fever spikes metabolism, aiding the immune system. More calories burn, says Scientific American.

Why does the Body Temperature Rises when there is Fever?

Nurofen states that fever is in fact the body’s weapon against infection. One of its symptoms is a high body temperature which occurs to help your body fight the bacteria or viruses that are causing the infection. When these enter the body, the immune system releases chemicals that make the hypothalamus increase your body temperature higher than normal.

What is the Hypothalamus?

Hypothalamus is the area of the brain that controls the following:

  • Temperature.
  • Hunger.
  • Thirst.

It is found at the base of the brain that is connected to the pituitary gland by a stalk made of both nerves and blood vessels, according to Hormones Australia. This sets the body’s temperature to normal if there is no bacteria or virus in the body.

What is the Normal Body Temperature?

According to Health Direct, a normal body temperature is within 36-37°C. However, it may be affected by the following factors:

  • Age.
  • Physical activities were done before measuring the body temperature.
  • Time of the day.
  • How the body temperature was done.

The same source stated that if the body temperature is measured to be 38°C or higher, you may have a fever.

How is Body Temperature Measured?

Measuring the body’s temperature may be done with the use of the following:

  • Glass thermometer.
  • Battery-operated tympanic (ear) thermometers.
  • Infrared forehead thermometers.
  • Fever strip thermometers.
  • Digital thermometer.

The last one may be the most commonly used in detecting a fever. It may also be added to first aid kits so appropriate first aid practices may then be applied as soon as possible.

Why Does Fever Cause an Increased Metabolism?

According to LibreTexts, once the fever increases the body’s temperature, there is then an increased rate of both enzyme reactions and metabolism. These occur in order to do the following:

  • Increase the production and activity of phagocytes.
  • Speed up the multiplication of lymphocytes.
  • Increase the rate of antibody and cytokine production.
  • Increase the rate at which leukocytes are released from the bone marrow into the bloodstream.
  • Speed up tissue repair.

All of which are the methods of how the immune system fights an infection.

How Many Calories Are Burned When There is a Fever?

Mel Magazine cites that in every 0.5°C increase in body temperature, your basal metabolic rate increases by around 7%.

Mel Mag: Each 0.5°C rise in body temp boosts basal metabolic rate by 7%.

What is a Basal Metabolic Rate?

Also known as the BMR, it is the rate at which the body calories (energy) while at rest to perform vital functions such as:

  • Breathing.
  • Keeping the body warm.
  • Heart rate.
  • Brain function.

There is no uniform BMR for all persons as it depends on many factors.

What Factors Affect the BMR?

The BMR may be affected by:

  • Muscle mass.
  • Age.
  • Body size.
  • Gender.
  • Genetics.
  • Diet.
  • Physical activity.
  • Hormonal factors.
  • Environmental factors.

Since these may change from time to time, BMR may also vary throughout the day, the week, the month, or the year. However, there is still an identified average BMR for men and women.

What is the Average BMR?

Better Health states that the BMR, which is measured in kilojoules (kJ), is estimated to be at an average of around 7,100 kJ/day for men and 5,900 kJ/day for women.

What are the Average Calories Burned per Day?

Kilojoules (kJ) may be converted to calories and according to the Calculator Site, it is done with the formula kJ = calories (kcal) × 4.184. So, with the above-mentioned average BMR, it is:

  • Men = at least 1,696.94 kcal/day
  • Women = at least 1410.13 kcal/day

Remember that these are only for performing vital functions. Calories needed to perform other tasks such as walking, exercising, talking, etc. are not yet accounted for.

What is the New BMR When there is Fever?

If body temperature is at 38°C if there is fever, there is at least a 1°C increase, therefore:

  1. Men
    -7,100 kJ/day + 14% of BMR = at least 8,094 kJ/day BMR if there is a fever.
  2. Women
    -5,900 kJ/day + 14% of BMR = at least 6,726 kJ/day BMR if there is a fever.

This means that for men, an additional 994 kJ/day is added while it is 826 kJ/day for women when there is a fever.

How Many Additional Calories are Burned When there is a Fever?

Using the Calculator Site, it is:

  • Men: 237.57 calories/day
  • Women: 197.42 calories/day

Calculations are still based on the average BMR for men and women mentioned above.

Does Fever Cause Weight Loss?

As per the sample calculations above, there is an additional number of calories burned when there is a fever. These may not be likely “eaten back” by someone who has a fever as there may be a loss of appetite and tiredness. According to Mayo Clinic, when someone eats fewer calories than the average required per day, he/she may end up losing weight. It may just be one of the many effects of fever that may be unhealthy.

What are the Possible Effects of Fever?

Aside from a possible unintentional weight loss, fever may also lead to the following:

  • Febrile Convulsions.
  • Dehydration.
  • Severe headache.
  • Skin rash.
  • Stiff neck.
  • Vomiting.
  • Shivering.

All of which including the fever itself may be treated with first aid. If it persists, going for a check-up is advised as it may be a symptom of a serious sickness or disease, like Covid-19.

What is the First Aid for Fever?

The first aid response to fever may be:

  • Drinking plenty of water to avoid dehydration.
  • Dressing in lightweight clothing.
  • Use a light blanket if you feel chilled, until the end of the chill.
  • Take paracetamol or medicine as prescribed by a doctor.

On the other hand, first aid management for the above-mentioned possible effects of fever may be learned from a first aid course in 123C Colin St West Perth 6005.

Fever first aid: rest, fluids, cool compresses.


You can burn more calories when you have fever since it causes the metabolism rate to increase. It occurs as an effect of performing additional functions in the body to fight bacteria and viruses. Fever may also cause a loss of appetite and tiredness, leading someone to eat less than the usual or average food intake per day.

When this happens, a person consumes fewer calories than what the body requires which may lead to weight loss. It is one of the possible effects of fever that may be unhealthy and may be needed to be responded to with first aid. If a high fever persists, it may be a symptom of another serious sickness or disease so going for a check-up is advised.

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