Longevity 8 MIN READ

Why is core body temperature a big deal?

Why does a hot cup of tea feel so good after you’ve been drenched in the rain? Or when it’s hot outside, all you want is a refreshing cold beverage?

Written by Priti Noronha

Apr 12, 2022
body temperature bigdeal

Why does a hot cup of tea feel so good after you’ve been drenched in the rain? Or when it’s hot outside, all you want is a refreshing cold beverage?

Knowingly or unknowingly, we are always trying to make ourselves comfortable by regulating our body temperature. But the need to maintain a certain body temperature is also about keeping healthy and fit.

Your body temperature can reveal a lot of things about your body—whether you have an illness, stress, sleep issues, compromised metabolism and more. Let’s further our understanding of our body temperature and learn more.


  • Our bodies have an internal thermostat that works continuously to keep internal temperature conditions constant,
  • Core body temperature refers to the temperature of the body’s internal organs, such as the heart, liver and brain, and blood,
  • Peripheral temperature is the temperature of the body as recorded at the surface level, i.e., on the skin.

Understanding thermoregulation, the body’s internal thermostat

Our bodies have an internal thermostat that works continuously to keep internal temperature conditions constant. This process is known as thermoregulation and it allows the body to maintain its core internal temperature.

Thermoregulation is controlled by the section of the brain known as the hypothalamus. When your internal temperature starts to become too low or high, the hypothalamus sends signals to your muscles, organs, glands and nervous system which, in turn, respond in different ways to help your body return to normal temperature.

The following 2 processes help the body cool down:

1. Sweating

Sweat glands release sweat, which cools the skin as it evaporates, thus helping lower internal temperature.

2. Vasodilatation

The blood vessels under the skin get wider, increasing the blood flow to the skin where it is cooler and away from the warm inner body. This lets the body release heat through heat radiation.

The following 3 processes help the body to heat up

1. Vasoconstriction:

The blood vessels under the skin become narrower, decreasing the blood flow to the skin, thus retaining heat near the warm inner body.

2. Thermogenesis:

The body’s muscles and organs and the brain start producing heat in a variety of ways. For example, muscles will produce heat by shivering.

3. Hormonal thermogenesis:

The thyroid gland releases hormones to increase the body’s metabolism. This increases the energy the body creates and the amount of heat it produces.

Interestingly, our bodies can have two different temperatures at the same time. Let’s find out how.

Core body temperature vs peripheral temperature

Body temperature can be broken down into core body temperature and peripheral body temperature.

Core body temperature refers to the temperature of the body’s internal organs, such as the heart, liver and brain, and blood.

Peripheral temperature is the temperature of the body as recorded at the surface level, i.e., on the skin.

When we want to know if someone has a fever coming on, we place our hand on their forehead; the temperature that we are feeling then is peripheral temperature.

Core body temperature readings can be obtained in a number of ways: inserting a thermometer into the rectum, inserting a thermistor (a resistance thermometer) in the oesophagus, using infra-red sensors to measure the temperature of the tympanic membrane (eardrum) of the ear, measuring the temperature of the urine and inserting a catheter into the pulmonary artery.

Out of all these methods, pulmonary artery readings are considered to be the gold standard for measuring core body temperature, as the artery carries blood directly from the core of the body.

These readings are used in situations where accuracy is absolutely crucial (for example, intensive care units, surgeries, etc.).

Peripheral body temperature (skin level’ temperature) is commonly measured at non-invasive sites such as the mouth, ear and armpit because these areas are easily accessible and are believed to provide a rough estimation of the core body temperature.

There are many factors that affect the accuracy of peripheral body temperature measurements—recent consumption of food, smoking, wax build-up in the ear canal, perspiration in the armpit, etc.

Usually, there can be a difference of as much as 1–2 degrees between the actual core body temperature and peripheral temperature measurement.

A rise in body temperature can mean an onset of fever, where the body is trying to kill a virus or bacteria that is causing an infection.

Certain medications and drugs can also cause a rise in body temperature.

Among women, perimenopause or menopause can cause hot flashes and night sweats, both of which temporarily elevate body temperature. There are a few interesting facts about body temperature you should know.

What is a normal body temperature range and is it time to reconsider it?   

A healthy normal human temperature is generally accepted as 98.6°F (Fahrenheit) or, if you measure body temperature in Celsius, 37°C.

It can also range between 97.7°F (36.5°C) and 99.32°F (37.4°C). While this has been accepted as the standard since the 19th century—when a German physician, Carl Wunderlich measured axillary (armpit) temperatures from about 25,000 people and found that the average body temperature was 98.6˚F (37˚C)—recent studies have shown that for a typical adult, body temperature can be anywhere from 97°F to 99°F and for babies and children, from 97.9°F to 100.4°F.

This suggests that it might be time to redefine the range of the base temperature of the body.

However, what is the reason behind the average body temperature changing over the decades?

There are two possible answers.

In the 19th century, when the ideal body temperature was first determined, diseases like tuberculosis, syphilis, chronic gum disease and other inflammatory conditions were very common.

These conditions typically raise the body temperature. Since treatments weren’t as readily available at the time, it’s fair to assume that a lot of people normally had higher body temperatures.

With improvements in medical science, these conditions became less prevalent, thus reducing the average body temperature.

Another possible reason could be a low metabolic rate. One of the biggest factors in determining body temperature is our metabolic rate.

Just like an idling car engine that still burns fuel, your body expends energy even when it’s not doing anything, which generates heat.

Heat is both a byproduct of metabolism and a form of energy that determines the speed at which metabolism occurs, otherwise known as metabolic rate.

A higher metabolic rate will produce more heat, thus increasing body temperature. A lower metabolic rate in modern times could be due to higher body mass (some studies link lower metabolic rate with obesity), or better medical treatments and overall metabolic health.

Generally speaking, it’s normal for your body to have a slightly higher temperature (around 99°F), as it’s an indication that your body is working to keep you healthy from an infection. However, a lower body temperature (below 95°F) may mean that something is not quite right.

Some of the medical conditions that can cause a dip in your body temperature include an underactive thyroid (hypothyroidism) or low blood sugar (hypoglycemia). Let’s look further into this phenomenon.

Why you should aim for a slight increase in your core body temperature?

Research over the years has shown that a warm body is better than a cold one. According to Professor Ariaki Kawashima of Tokyo Ariake Medical University and a doctor at the Tokyo Medical Research Institute, the optimal human body temperature still stands at 37°C/98.6°F.

However, most people today have body temperatures that are still about one degree less. While one degree may not seem much, in reality, it may cause the body’s metabolic capacity to decrease by about 12-120% and its immune function to down by at least 30%.

When our body temperature starts to lower, the concentration of blood increases and its circulation deteriorates. Poor blood circulation means nutrients and oxygen don’t reach the various parts of our body, including our inner organs, efficiently.

This may cause disruption in the production of hormones and neurotransmitters. Moreover, we become less immune to viral infections when our body temperature is lower. Hence, we often fall sick during cold and rainy weather.

How can we increase our body temperature in three ways?

1. Heat therapy

Today, there are various ways in which medical practitioners use heat as a form of curative therapy. One of them is Onnetsu therapy, an autoimmune health care method that warms up the body using heat (far infrared waves) through physical stimulation which, in turn, helps blood circulation to improve health. It has been used to treat conditions like arthritis, cancer, diabetes, osteoporosis, Parkinson’s disease, Hashimoto’s disease, hypothyroidism and more. There are also other methods of heat therapy that are more easily accessible. Thermotherapy is the use of basic tools such as hot clothes, hot water bottles, heating pads, etc., to alleviate pain and inflammation, muscle spasms and decrease joint stiffness.

2. Moderate to strenuous exercise

Exercise is not just about losing weight. When you exercise, your heart rate increases and pumps up the circulation of blood and oxygen in your body. These physiological processes not only preserve homeostasis in your body but also help boost your body temperature, blood oxygen levels, sugar levels and hydration.

3. Right diet

Your body produces heat as it digests and metabolizes your food. This process is called thermogenesis. Although alcohol and caffeine increase heat in the body, they’re definitely not the healthiest options to keep yourself warm. Foods like oats, ginger tea, chillies, sweet potatoes and bananas are all great options for regulating your body temperature.


In conclusion, an ideal body temperature is essential to your immune system and to keep your body moving smoothly. The optimal human body temperature stands at 37°C or 98.6°F, although it can be slightly lower or higher depending on the environmental factors. To ensure that your immune function performs at full capacity, it’s always better to have a slightly higher temperature than a lower one, and exercise and the right diet are the best way to go about it. 

Disclaimer: The contents of this article are for general information and educational purposes only. It neither provides any medical advice nor intends to substitute professional medical opinion on the treatment, diagnosis, prevention or alleviation of any disease, disorder or disability. Always consult with your doctor or qualified healthcare professional about your health condition and/or concerns and before undertaking a new healthcare regimen including making any dietary or lifestyle changes. 


  1. Core body temperature v peripheral body temperature
  2. Core temperature measurement: Methods and current insights
  3. Time to redefine normal body temperature?
  4. Rapidly declining body temperature in a tropical human population
  5. Onnetsu Far-Infrared Therapy

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