Our bustling lifestyles have contributed to the increasing prevalence of obesity and its associated medical problems. Sure, we appreciate the need for activity and healthy eating but in reality many of us prioritise convenience and speed. Among the plethora of modern conveniences we have cars (self-driving anyone?), microwaves, smartphones and fast foods including quick home deliveries. It’s quite easy to see how these can lead to unhealthy and sedentary lifestyles.

More recent studies are suggesting that even the usage of heating and air conditioning systems can lead to weight gain. This is bad news if you’re experiencing bitterly cold winters or unexpected heatwaves. So, why would using a heater or an air conditioner promote weight gain? Should those seeking to lose weight avoid these amenities? Why should subject ourselves to uncomfortable temperatures? Let us first learn how our bodies regulate temperature.

Understanding thermoregulation

When was the last time you were shivering due to cold weather? Do you remember sweating profusely due to heat? These days many of us have stopped shivering or sweating with the excellent heaters and air conditioners installed in our houses and flats.

It is interesting to note that people may also sweat or shiver due to fear! Fear and its implications for weight loss is a subject we will be discussing in another article.

Temperature plays a crucial role in keeping us healthy. To help our body maintain a healthy internal body temperature, the hypothalamus in the brain controls body temperature. Thermoregulation is a process that checks and balances our core body temperature. The average body temperature is between 98°F (37°C) and 100°F (37.8°C).

When your body temperature falls to 95°F (35°C) or lower, you experience hypothermia, which can potentially lead to cardiac arrest, brain damage, or even death. People are known to suffer from heat stroke when their core temperature rises above 104°F (40 °C). Heat stroke is more often encountered in summer months. Left untreated, heat stroke could result in confusion, agitation, delirium, seizures and even coma or death. 

Whenever our body temperature alters due to internal changes, like an infection, or external factors like heaters or air conditioners, the hypothalamus sends signals to the muscles, organs, glands, and nervous system. The body auto-corrects and brings about a state of equilibrium (known as homeostasis) in our core temperature. This explains why you sweat to bring your body temperature down during a fever. As long as humidity levels are appropriate, the sweat evaporates from your skin to cool you down. Try not to wipe away the sweat with a towel as this mechanism only works if you allow sweat to evaporate from your skin.

If you are cold, the body has natural ways to produce heat and keep you warm. This is known as thermogenesis. The most common way is by shivering; the impulse to shiver in the cold causes muscle fibres to generate internal heat. Non-Shivering Thermogenesis (NST) uses metabolic processes and brown fat to generate heat. This process is mainly regulated by hormones produced by the thyroid and adrenal glands.

Recent studies reveal how excessive exposure to heaters and air conditioners could lead to weight gain.

How do heaters promote weight gain?

According to researchers from University College London and the University of Cambridge, an increase in indoor temperature could reduce the calories we burn to stay warm and lead to storage of excess energy as fat. The researchers called it the “thermal comfort zone”. Modern homes in North America, the United Kingdom and Europe are equipped with heaters and are well insulated. This could be one of the reasons for the obesity pandemic in the West.

While poor diet and sedentary lifestyle are major causes of obesity, dependence on heaters could affect weight gain. So, where is the evidence?

The authors presented a hypothesis that people’s exposure to low temperature in winter months allows the body to use up calories, burn fat and generate heat. It also improves thermogenesis. However, this natural process is disrupted when heaters adjust the temperature and the body is not allowed to naturally regulate internal temperature. Fiona Johnson, a research fellow at University College London and the paper’s lead author, said that people tend to use heaters in every room and most have now installed centralised heating systems in their homes. A few decades ago, heaters were only used in living rooms. Today, heaters are installed in every room, in cars, shopping centers and even gyms or pools. People choose to either stay indoors or prefer to visit places which have adequate heating facilities during cold weather. Children are also encouraged to stay indoors instead of going out.

As we mentioned earlier, heat is not just generated by shivering but also by non-shivering thermogenesis. This is carried out by a specialised tissue call the Brown Adipose Tissue (BAT). Research has shown that aging and living in a heat controlled environment can reduce BAT in the body and hence reduce heat production. BAT can be activated by exposure to cold weather.

Fiona Johnson says: “If you’re not exposed to cold, you’re going to lose your brown fat, and your ability to burn energy will be affected”.

What about air conditioners?

If heaters can hinder thermoregulation, so can air conditioners. People switch on their air conditioners or cooling fans when it is hot. The resulting drop in room temperature keeps your body in a comfortable zone where it doesn’t need to work hard and produce sweat.

Air conditioners were previously designed for industrial places to ensure the electronic machines work better and you have a conducive working environment.

According to a study published in 2006, in the International Journal of Obesity, the southern part of the United States had one of the highest obesity rates between the years 1978 to 1997 and during this period there was an increased use of centralised air conditioners. Installation of domestic air conditioners increased from 37 to 70 percent during those twenty-years. Today, air conditioners are present in many homes, most cars and almost certainly found in public places like offices, restaurants, shops and cinema theatres.

Most studies reveal an observational effect between weight gain and heating/air conditioning systems. More research needs to be done to prove a direct causal effect of these systems.

Finding comfort in food

In addition to using temperature controlling devices we also use certain foods to regulate body temperature.

During summer we prefer ice creams and cold milk shakes to keep us cool. Similarly we opt for warming, starchy meals and hot drinks during winter. Your body craves for appropriate food to keep you comfortable. They may keep you comfortable during unfavourable weather but you may struggle to burn it off.

Instead you could try herbal teas or cold water tinged with the flavour of cucumber, lemon or some other fruit blend.

What should I do?

Go natural! Let your body sweat when needed and allow your body to shiver when it is cold. If you are very uncomfortable go ahead and use available resources but limit your time with them. However, do take care of yourself if you are unwell or undergoing any treatment.

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