The good body fat that holds the key to keeping weight off (and how to activate yours)

Telegraph

01-04-2025

It is the 'good' fat which can help us lose weight rather than gain it. Now new research has found that the brown adipose tissue (BAT) which is rich in mitochondria, could promote longevity and help keep us healthy as we age.
The Rutgers New Jersey Medical School study found that mice lacking a specific gene developed an unusually potent form of BAT that expanded lifespan and increased exercise capacity by 30 per cent.
The genetically modified mice, which lack a protein called RGS14, lived around 20 per cent longer than normal mice and avoided typical signs of ageing including hair-loss and greying. Their BAT also protected them from obesity, glucose intolerance, cardiovascular disorders, cancer and Alzheimer's disease.
The team is now working on a drug that could mimic these effects in humans. 'Exercise capacity diminishes as you get older, and to have a technique that could enhance exercise performance would be very beneficial for healthful ageing,' said Prof Stephen Vatner, the study's senior author.
What role does brown fat play?
Most of the fat in our bodies is white tissue, distributed around our waist, hips and thighs. But most adults have around 100g of brown fat, too, according to Prof Michael Symonds, the deputy head of the University of Nottingham School of Medicine, mainly stored around our necks and also found in the collarbone and spine.
Studies suggest it is only detectable in a minority of people – possibly as few as 10 per cent – but currently, the only way to know how we compare is via a positron emission tomography (PET) scan, which involves injecting radioactive material into the body and is usually used to diagnose cancer.
The primary function of brown fat is to provide warmth: it produces 300 times more heat than any other tissue in the body. It is first activated in newborn babies to protect them from the shock of exposure to the cold after birth. As we age, the amount of brown fat in our bodies declines. But it would be helpful if we could hang onto it or increase the levels we have.
Research has shown it has numerous health benefits, including better blood sugar control – decreasing the risk of Type 2 diabetes – higher levels of 'good' cholesterol and a decreased risk of fatty liver.
A study of over 52,000 participants by The Rockefeller University in New York also found a strong link between having detectable brown fat and a reduction in coronary heart disease, heart failure and high blood pressure.
Brown fat has a unique protein – the uncoupling protein 1 (UCP1) – which makes it different from white fat. This protein is present on the inner mitochondria, and when it's stimulated, it produces heat.
'To make heat, brown fat requires a lot of energy in the form of lipids [fats] and sugar,' says Toni Vidal-Puig, a professor of molecular nutrition and metabolism at the University of Cambridge. 'It burns this excess fuel – meaning that the more brown fat you have, the higher your capacity to remain lean.
Intriguingly, the Rockefeller University study also suggested that if obese people have detectable brown fat, it can protect them from the harmful effects of their white fat. 'It acts like a vacuum cleaner preventing the nutrients [from the fats and sugar] going to the liver, the arteries and muscles,' says Prof Vidal-Puig.
As a result, researchers are working to find a way to harness brown fat to 'prevent the complications associated with obesity', he says.
The drug Mirabegron, used to treat an overactive bladder, has been shown to activate brown fat, but it also raises blood pressure. Researchers are exploring whether smaller doses of the drug taken over long periods will be enough to stimulate brown fat without significant cardiovascular risks.
In the meantime, there are ways to safely activate brown fat through lifestyle changes.
Spend two hours a day in the cold
The brown fat protein, UCP1, 'isn't innately active; it has to be activated,' says Roland Stimson, professor of endocrinology at the University of Edinburgh.
Perhaps the most efficient way to do this is through cold exposure. One study in Maryland involved five healthy 21-year-old men spending 10 hours per night in a room with the temperature set to 19C. After a month of this exposure to mild cold, they had a 42 per cent increase in brown fat volume and a 10 per cent increase in fat metabolic activity.
Turning the thermostat down at night, then, could be a simple way to activate brown fat. And if that sounds too punishing, according to Prof Stimson: 'We've seen from the controlled studies that even mild cold exposure of 17C for two hours a day is sufficient to expand the function of your brown fat.'
Take a cold shower
Immersion in cold water is also beneficial. ''Three or four minutes in a cold shower every morning, or a cold water swim a few times a week will activate brown fat and may be helpful in keeping excess weight off,' says Prof Symonds. In 2008, researchers at Maastricht University found that Wim Hof, the Dutch extreme athlete known for his ability to withstand freezing temperatures, had built up so much brown fat he could produce five times more heat energy than the typical 20-year-old.
Cold water also helps boost your immune system, increases endorphins and improves circulation, making it a particularly positive habit to adopt.
Drink a daily cup of coffee
A first-of-its-kind 2019 study by Prof Symonds and his Nottingham University team suggested that drinking a cup of coffee can stimulate brown fat.
The team used a thermal imaging technique they pioneered to trace the body's brown fat reserves, then used it again immediately after participants had drunk the coffee to see if the brown fat became hotter. 'The results were positive,' says Prof Symonds.
The team are conducting further research to ascertain if caffeine supplements have a similar effect. In the meantime, he says: 'Drinking 10 cups of coffee a day won't prevent you from having a weight problem, sadly, but as part of a bigger picture, it's certainly worth adding a coffee into your daily routine.'
Eat spicy food and drink green tea
Research by Japanese scientists has shown that capsinoids, the compounds found in chilli peppers and some types of red peppers, activate brown fat – so adding spice to your meals may help you stave off excess pounds.
Other foods which have been shown to stimulate brown fat include green tea, which is rich in catechins, a type of flavonoid and polyphenol known for its strong antioxidant properties. Another Japanese study looked at participants who had ingested catechins and caffeine in the same drink and found it 'acutely increases EE [whole body energy expenditure] associated with increased BAT [brown adipose tissue] activity'.
Eat more mackerel
Omega fatty acids have also been shown to positively impact brown fat, particularly docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), which are primarily found in oily fish such as salmon, tuna, mackerel and sardines. Fish oil supplements are a good idea for those who don't eat seafood.
Ursolic acid, an anti-inflammatory, antioxidant compound found in plants including apples, rosemary and thyme, has been shown in mice studies to increase brown fat and energy expenditure. Other studies involving mice suggest ginger can also induce browning in white fat – in other words, turn unhealthy white fat into beneficial brown fat.
Don't starve yourself – or binge
Researchers at the Yale School of Medicine found that in mice, the neurons in the brain which regulate hunger can encourage fat to turn brown.
The study found that eating too few calories prevented white fat from turning brown, while eating just enough to satisfy hunger stimulated the neurons and turned the fat brown.
Conversely, eating too much can also cause harm, not only because it increases white fat, but because it could interfere with brown fat's ability to burn calories.