Humans are born with brown fat around their shoulder blades - it plays an important role in maintaining our body temperature as babies, by burning up calories and fat reserves to keep us warm.
Unfortunately, scientists have long thought that brown fat disappears in infancy once its physiological uses have been exhausted.
Then five years ago, brown fat was 'rediscovered' in adults, when researchers carrying out scans on adult patients in the winter months noticed areas of fat that seemed to be turned on by the cold weather.
Their scans detected a few ounces of brown fat in the upper back, on the side of the neck, in the dip between the collarbone and the shoulder, and along the spine.
Since then, brown fat has become a rapidly growing area of interest among researchers who believe it could hold a vital key to weight problems, the Daily mail reported.
It's now believed that not just the cold, but certain foods can also activate it. So, too, can exercise.
In a study published in the Journal of Pediatrics in June, Professor Michael Symonds Symonds has suggested some simple ways to activate brown fat in the body.
Turn down the heating and put on a jumper if you feel really cold, Professor Symonds suggested adding, "We need to feel the cold to burn calories."
Add chilli peppers to food - the active ingredient capsaicin has been shown to trigger brown fat into action, according to him.
He asked people, who want to lose weight, to avoid the gym and instead take a walk, go for a cycle or just skip outdoors on a cold day. Doing so can get brown fat working.
He said outdoor exercise of any kind is beneficial.
Dairy products - yoghurt, milk and cheese are thought to be important in activating brown fat.
But he warned people to avoid high-fat, sugary carbohydrates and highly processed foods as they may have an adverse impact on brown fat.
Drinking cold water or ice-cold juice may also provide the benefit, noted Professor Symonds.
Some studies have shown that cold drinks help to keep the body's core temperature lower during exercise - the effects might also trigger brown fat into action.