NOW IS THE TIME TO BUILD BROWN FAT

We turn the heating off at night, in our house. Manually.  And I’m an early riser. Which means that when I wake up – usually around 6am, often earlier – it’s both dark and very cold. Our house is old, with single glazed windows, so any residual heat from the previous day has invariably escaped by this time. Naturally it’s tempting to linger under the duvet. But I spent my formative years in a house without central heating, run by frugal parents who told us to put on more clothes. So I get up and shiver my way to the bathroom for my cold shower.

I’m no Wim Hof: I can honestly say that I dread that first blast of cold water. Especially when the bathroom feels like an ice box. But I feel great afterwards, fully awake and alive. And on the days when I really dread it (not enough sleep, bathroom colder than normal), I also remind myself about Brown Fat. Medically known as Brown Adipose Tissue (BAT), brown fat stores energy, burns calories, regulates blood sugar and insulin levels. It may do many other magically life-enhancing things. Indeed, researchers are desperately trying to concoct a pharmaceutical version of Brown Fat, because it appears to protect against obesity, heart disease, cancer, T2 diabetes and Alzheimer’s. Importantly, Brown Fat gobbles up the more dangerous, artery-clogging  White Fat.

At its simplest, Brown Fat exists to produce heat – and so keep us alive. Babies are born wrapped in a generous cloak of it, enabling them to stay alive for a little longer (presumably in the event that Mum was subsequently eaten by a tiger.)  It starts working before shivering sets in, producing warmth by breaking down glucose and fat molecules.

Which is why cold is the very best activator of Brown Fat. Cold showers aren’t the only way – I have a chapter in 52 Ways to Walk on how a wintry stroll activates the stuff, but you could also try keeping the thermostat down for short periods. Exercise also helps activate it, as does drinking coffee. Eating the right diet is important too – plenty of healthy fats, and sufficient iron.  Brown Fat is chock full of iron-laden mitochondria which is why it has a brown colour. Apples and herbs might help (see below).

An abundance of Brown Fat is thought to be one of the reasons that very old people (think centenarians) are always thin, and why longevity researchers consistently cite lean-ness as one of the strongest predictors of healthy longevity.  As we age, it’s unclear whether we lose or gain Brown Fat. Studies have found different outcomes. But one thing is clear: having plentiful supplies could help us all age well.

Just before Christmas, a new study of Brown Fat was published.  This study – from Rutgers New Jersey Medical School in the US – found that having more brown fat made it easier to exercise.  Which is to say that, not only might exercise activate Brown Fat, but that having plentiful brown fat might also make it easier to exercise.  This study was done in mice, but could it also apply to humans? The researchers confidently asserted that, yes, it could, noting that Brown Fat ‘enhances healthful aging.’

Here are a few tips on how to increase your own Brown Fat supplies:

Go for a regular wild swim

Take a cold shower or ice bath. The Cleveland Clinic suggests twice a week.

Go for a walk and expose your neck to the air for a few minutes.  Brown Fat collects around the neck, shoulders and chest.

Turn the thermostat down every now and then. You want to be feeling a little cool, not violently shivering.

Nor does it need to be bracingly cold – some studies suggest two hours of exposure to 66°F (19°C) is all that’s required.

Eat apples, specifically their peel, and other foods containing Ursolic Acid. A handful of studies suggest that this plant-derived phytochemical prompts the production of Brown Fat.

The herbs, rosemary, holy basil and sage are particularly rich in Ursolic acid. In fact many herbs – oregano, thyme etc – contain lots of Ursolic acid, so use them liberally in your cooking. This recipe  from our recipe archive is particularly herb-dense.  I’m quoting from Examine.com here: ’Although the science is preliminary, [ursolic acid] seems to reduce fat accumulation and increase muscle mass gain when in a fed state, and to induce fat burning and preserve muscle mass when in a fasted state.’

Eat plenty of good fats – avocados, nuts and seeds, for example.

Make sure you’re getting enough iron from food like meat, seafood, whole grains, leafy vegetables and beans. Sufficient iron will keep your fat cells healthy.

Drink caffeine – according to a 2019 study, caffeine activated Brown Fat.

Of course, we need more research.  The problem with cold exposure research is that most people don’t want to be part of it, or can’t maintain it.  So the bulk of the research still involves mice.  However, there are enough studies of human tissue to suggest that plentiful brown fat won’t hurt us – and may keep us healthier and happier for longer.  Or you can follow the advice of longevity guru, Peter Attia, who says it’s irrelevant whether ice baths and cold showers make you live any longer – what’s important is how they make you feel… better… now!

Interestingly, another cold therapy study crossed my desk recently.  According to this report, five minutes of cryotherapy resulted in an increase in slow-wave sleep, as well as improvements in mood and reductions in anxiety.  In this experiment, men and women spent five minutes a day in a cryostimulation chamber, chilling their bodies to -90C. Cold didn’t help them fall asleep more quickly and it had no effect on REM sleep, but deep slow wave sleep increased by an average of 7.3 minutes per night, with men and women responding differently. ‘The benefits were particularly noticeable for women’, noted the researchers.

Most of us don’t have access to cryostimulation chambers. And five minutes in a cold shower seems a long time, even by my standards.  I suspect there are easier ways to get that extra 7.3 minutes of deep sleep (a good long walk does it for me). But I mention it, just in case!

Perhaps more importantly, cold exposure activates immunity. We first wrote about this in our book The Age-Well Project.  Since my conversion to daily cold showers, several years back, I’ve barely had a cold. In the last year (during which I increased the duration of my shower to a good two minutes every morning), I’ve not had a single cough, cold, sniffle.  Studies published last year have continued to unpick why cold improves immunity.  It’s still a little hazy but a 2024 study of Egyptian adults found that those who cold showered had considerably higher levels of immunoglobulin, and more immune-boosting (and anti-cancer) T-cells.  The researchers concluded that ‘Regular cold shower exposure appears to enhance humoral and cell-mediated immunity.’  They proposed that cold induces physiological adaptations that prime the immune response, thereby boosting immunity. This makes evolutionary sense: faced with potentially debilitating or fatal cold, the body must do all it can to stay alive.

I think what I’m saying is this: it may be cold out there, icy water (or air in my house) may feel deeply uncomfortable, but please don’t spend the winter months locked up in your centrally-heated house. Embrace the (healing) cold!

Within reason, of course. And if you’re new to cold showers or wild swimming (or even exposing yourself to the cool), always check with your doctor first and start very, very slowly.

And for anyone who remains unconvinced, I’ll leave the final word to a group of scientists who, after examining all the evidence of previous studies, wrote:

“Deliberate exposure of the body to cold water results in distinct physiological responses that may be linked to several health benefits. Evidence, primarily from small interventional studies, suggests that cold water therapy positively impacts cardiometabolic risk factors, stimulates brown adipose tissue and promotes energy expenditure, potentially reducing the risk of cardiometabolic diseases. It also triggers the release of stress hormones, catecholamines and endorphins, enhancing alertness and elevating mood, which may alleviate mental health conditions. Cold water therapy also reduces inflammation, boosts the immune system, promotes sleep and enhances recovery following exercise. The optimal duration and temperature needed to derive maximal benefits is uncertain but current evidence suggests that short-term exposure and lower temperatures may be more beneficial. Overall, cold water therapy presents a potential lifestyle strategy to enhancing physical and mental well-being, promoting healthy aging and extending healthspan.”

If you’ve been enjoying these wintry months (apologies to our readers Down Under), please do share any tips for making the most of this season.  And let’s not forget that these cold snaps should be relished for other reasons too. With rising temperatures and continued climate crisis, it’s possible (God forbid) that our children will never see snow, or experience the wintry glitter and sparkle of frost, or feel their cheeks nipped pink by an icy wind. It’s a horrible thought, but let it spur you on and out – enjoy it while you can.

And if you know anyone who might be interested in the contents of this blog post, please pass it on.   We would be delighted!

Annabel