In the 16th century, a Swiss naturalist Konrad Gesner identified a mysterious organ in marmots that were neither muscle nor fat – but something distinctively ‘brown’ and unique. Thus began our centuries-long exploration of brown adipose tissue (BAT) – an extraordinary body part capable of generating heat directly from food ingestion. To this day, BAT remains a mysterious phenomenon and is believed to be a great booster of metabolic processes. Let’s find out more about this fascinating organ.
What is brown fat?
Many people don’t know about this unusual organ despite its very important and beneficial role in their metabolic health. Brown fat or brown adipose tissue (BAT) is a unique organ that can be activated to produce heat which helps regulate body temperature. It utilizes energy more efficiently if you feel cold. When the temperature drops or we take a plunge in cold water, it helps us feel warmer and it also keeps our body healthy during activities like eating, sleeping, running, or staying outdoors during cold weather.
How does brown fat work during cold exposure?
Cold temperatures act as a biological trigger with the body launching into action to protect itself. When skin receptors sense cold and activate the sympathetic nervous system – this is why our hands, feet, and face chill first upon contact with cold water or air. At this moment, skeletal muscles and brown fat activate, burning energy in order to generate warmth.
When our bodies experience the ‘cold shock’ the temperature regulation centre in the hypothalamus increases the release of norepinephrine – the alertness hormone. It sends signals that prime brown fat for heat production. BAT starts working on ‘fuel’ from sugar and fat from bloodstreams all around the body reducing unhealthy levels of both.
Brown fat improves insulin resistance and helps fight obesity
It’s been proven that brown adipose tissue activation improves glucose homeostasis and insulin sensitivity. Activation of brown adipose tissue via cold exposure has been linked to increased levels of circulating adiponectin. It is a hormone involved in regulating glucose levels and fatty acid breakdown. Scientists noticed that centenarians – people who live over 100 years old – and their offsprings have genetic advantages that result in higher concentrations of plasma adiponectin. So that might be another perk of brown fat power.
It also works perfectly against inflammation development caused by atherosclerosis when exposed to freezing conditions.
One of the studies on brown fat showed a great example of how the tissue can affect metabolic health.
A 2014 study involved a group of healthy young men that were wearing a cooling suit at 10°C (50°F), 2 hours daily 5 days a week. After a month, their brown fat volume increased 45% from the baseline.
Moreover, the oxidative metabolism in their brown fat increased more than two-fold, which supports the hypothesis that cold exposure increases energy expenditure and brings metabolic benefits.
What is the difference between brown and white fat?
Not only does brown fat looks different from other fats, but it also has a different structure. Scientists agree that the beige color of the brown adipose tissue is due to the fact that there are more mitochondria in brown fat cells than in white fat cells. As many remember from the school lessons, mitochondria is the ‘powerhouse’ of cells and the main engine of metabolism in them.
BAT stores fat inside its cells temporarily. It draws fat from the bloodstream and utilises it to make us feel warm. White fat tissue, on another hand, stores fat for longer periods of time and releases it slowly when a person hasn’t eaten for some time.
Where brown fat can be found?
Scientists have found that the reserves of brown fat in humans are located around clavicles and along the spine. Surprisingly, they also found small amounts close to both our hearts and kidneys. In infants, it is concentrated between their shoulder blades.
This tissue was discovered almost by accident during a positron emission tomography/computed tomography (PET/CT) scan. Such a scan is still the best method for visualizing brown fat. In infants, BAT makes up 2-5% of their total body weight. It has been estimated to range from 200-1500 g in adults – though some may have none at all! Unfortunately, even such a vital asset can fade away over time.
Brown fat and age
From the moment we enter this world, our bodies are equipped with brown fat.
In the past, adult brown fat was thought to be a minor player in our human tissue. Scientists assumed only newborns had significant amounts of it and used this special type of fat for staying warm since their muscles were not yet able to shiver. However, due to PET/CT scans conducted during the 1970s, researchers discovered that adults also possessed brown fat even as they aged – changing the scientific understanding completely. Scientists came to the conclusion that this organ must be critical if adult people didn’t ‘get rid of it’ in the process of evolution.
As age increases, the mass of brown fat typically diminishes – perhaps due to an enhanced surface area-to-body ratio which reduces temperature fluctuations. While its primary function is fading in importance, research indicates healthy adults under 40 still possess stores of this calorie-predator organ and that it may help us maintain a more consistent body weight throughout our lifetime. This is especially crucial since extra pounds are often gained over time.
Why do some
lucky people have more brown fat than others?
Studies indicate that regular activation of brown fat reserves helps keep them healthy and strong just like any other muscle that requires physical exercise for growth. Investing energy into maintaining these necessary fats could mean improved health overall.
Diabetes and obesity can lead to a dramatic decrease in brown fat, sometimes even total absence. This is unfortunate as this tissue has incredible potential for regulating metabolic rates and body weight. It may be that the lack of brown fat causes issues with both metabolism and weight gain – more studies need to be conducted on that issue.
Fun & Interesting facts about brown fat
Bats and naked mole rats have remarkably high levels of brown adipose tissue. Scientists assume that might be a reason for their metabolic health and incredible lifespans – 30-32 years, which is unusual for small mammals.
Brown adipose tissue glucose uptake is 8-fold higher than that of skeletal muscles during mild cold exposure.
Let’s summarise: Why should we activate our brown adipose tissue?
It’s pretty simple – apart from helping to survive the cold, brown fat burns down excessive amounts of energy stored in sugar and fat. Overconsumption of energy is what causes people to gain extra weight and leads to obesity, which is the main cause of many health issues. Keeping your metabolic health strong is really important for your overall health and brown adipose tissue can be a secret weapon in this battle. But to do that, you have to activate it and cold exposure is currently the best method to do that naturally and for free.
Hungry for knowledge? Here is more
If you want to learn more about cold exposure and the ways to activate brown fat, we recommend you read the book ‘Winter Swimming: The Nordic Way Towards a Healthier and Happier Life’. Dr. Susanna Søberg, the author of the book, practices cold exposure herself and has done multiple studies on the subject.
Watch this excellent short lecture from Dr. Rhonda Patrick on the metabolic effects of cold exposure, in which she explains the role of brown fat cells in thermogenesis and metabolic health.
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