Everyone knows that too much fat makes us fat. But it seems more of the right kind could make you thinner – and that fat is brown fat.
This is one of the two types of fat found in the body. There is the more familiar white stuff, which sits under the skin on your tummy and thighs and is the result of eating too much.
Then there is brown fat – and its job is to generate heat. It does this by boosting your metabolism, so you then start to use up the ‘bad’ white fat.
It’s long been known that babies have brown fat around their shoulder blades to help them maintain their body temperature after birth. But until recently it was thought this good fat disappeared in infancy because it was no longer needed.
Now it’s been shown that brown fat persists into adulthood. Not only that, some people – generally lean types – have more brown fat than others. This could help explain why they remain a healthy weight without much effort, while others struggle to lose weight.
In fact, scientists think boosting brown fat stores could be a new approach to dealing with excess weight.
‘We calculate that if you had three ounces of brown fat that was maximally stimulated, it could help you burn an extra 400 to 500 calories a day,’ says Dr Aaron Cypress of the Joslin Diabetes Centre in Boston.
He led one of three studies on brown fat recently published in the influential New England Journal of Medicine.
This research has also suggested that brown fat plays a role in diseases such as diabetes that are linked to obesity.
In some studies, stimulating the production of brown fat in mice stopped them gaining weight, or developing Type 2 diabetes, even when they were fed a high-calorie diet.
The good news is that many of us have brown fat. Around half of all people have deposits of it in their neck, where it is most easily detected, says Dr Cypress.
And women have more brown fat than men. It becomes activated and starts to burn fat naturally only when people are cold and on the verge of shivering.
In evolutionary terms, brown fat developed to protect newborn babies from lifethreatening cold temperatures. It is thought that, in a throwback to our ancestors, chilly conditions trigger brown fat to become activated in adults.
To demonstrate this, Sven Enerback, a researcher at the University of Goteborg in Sweden, kept five volunteers in a cool room for two hours before giving them a PET (Positron Emission Tomography) scan, which lights up any part of the body that is using glucose stores for energy, and not fat.
Enerback asked the subjects to place a foot intermittently in a bucket of icy water to chill their body, in the belief that it would trigger any brown fat to be revealed by the scan.
Brown fat deposits showed up each time their body temperature dropped. In another study, in Holland, a group of 24 men sat in a room cooled to 61F for two hours.
When they had PET scans, 23 displayed activated brown fat deposits; only the heaviest man had none.
The men were retested when they’d warmed up again; no brown fat was active. Scientists are investigating whether it is possible to reproduce this effect using drugs.
Professor Mike Cawthorne, director of metabolic research at the University of Buckingham, who has researched the effects of brown fat, says a drug to mimic the weight-loss benefits ‘is definitely on the cards’.
Another possibility is that a sample of a person’s brown fat could be removed from the body; this sample could then be increased in the laboratory and then re-injected.
There is another possible option for the half of the population who don’t have brown fat. Scientists have discovered a way to reproduce the energy-burning fat by manipulating mouse and human cells to produce it.
In a study published in Nature journal last month, Professor Bruce Spiegelman of Boston’s Dana-Farber Cancer Institute injected mice – which have lots of brown fat cells – with extra ‘good’ fat. He found it boosted their metabolism and burnt calories at a faster rate.
Injecting 50g to 100g of brown fat cells into a person could help them to burn off more than 10lb of ‘bad’ fat a year, say scientists.
But could there be a simpler solution? According to Professor Cawthorne, the brown fat levels of our hunter-gatherer ancestors would almost certainly have been more highly activated than our own.
Warmer temperatures, abundant food and too little activity have effectively switched off its usefulness in the modern world.
‘Even 30 years ago, it was more difficult to stay warm than it is now,’ says Professor Cawthorne. ‘Today, our homes, cars, offices, shops and almost everywhere we go are warm.’
Just turning off the central heating could help spur brown fat into action. ‘If we were to expose ourselves to cooler temperatures more often, then a lot of people would probably lose weight,’ he says.
‘Either that or have a daily sauna and plunge into icy water afterwards. Don’t have the heating on in the car and spend more time outdoors, especially in winter. We need to activate brown fat and there are simple ways to do it that may have some benefit.’
Source: Mail Online. Aug 18 2009