Embrace the Cold

Why winter is good news for your health

With the New Year bringing icy winds and frosty temperatures, it’s tempting to kick your runners and binge on boxsets instead. But new research suggests regular exposure to the cold could deliver an avalanche of surprising health bene ts, helping you to torch more ab, re up your metabolism, reduce your risk of diabetes, strengthen your heart and lungs, train harder and even ght o depression. “Exposing yourself to thermogenic stress encourages growth,” explains Scott Carney, author of What Doesn’t Kill Us, a bestselling exploration of environmental conditioning and the bene ts of cold exposure. “at could be psychological growth, which always happens when you're undergoing stress. Or it could be what we call ‘hormesis’, which is when you put yourself in a challenging situation and your body rises to the challenge by adapting. We’re talking about a ‘global’ change in your body here. It’s not only about metabolic changes that burn extra fat, but also psychological changes that can build resilience and ght anxiety.”

ADAPT AND OVERCOME

Your body is an amazing machine, and it has an innate evolutionary ability to adapt to di erent conditions. Although we now spend most of our time sitting in arti cially warm buildings, many of the physiological changes triggered by regular cold exposure can actually help to ne-tune the human body. When you’re exposed to the cold, your heart rate and metabolism increases, so you burn extra fat to keep warm. Your heart and lungs have to work more e ciently to pump blood and oxygen around your body. Glucose is released into your blood stream to encourage muscle activity – whether through shivering, or the urge to move and exercise in order to stay warm. Oxygen oods to the brain, delivering a powerful surge of clarity and alertness. And your brain releases the hormones beta-endorphin and noradrenaline to boost your energy and your mood.

e health e ects of these invisible adaptations are astonishing. Research in the American Journal of Human Biology suggests that winter hikes burn 34 per cent more calories. A study in the journal Diabetes found that simply sleeping in a cooler bedroom (19°C) raises your metabolism by ten per cent. Another paper

“Winter hikes burn 34 per cent more calories”

in the Journal of Clinical Investigation found that even mild cold exposure – two hours a day at 19°C for six weeks – cut subjects’ body fat by 5.2 per cent. A study in the journal PLOS One revealed that people who take cold showers are 29 per cent less likely to call in sick for work. And research by Cambridge University suggests cold-water swimming could even protect against dementia.

Carney discovered many of these health bene ts for himself when he experimented with the unique cold-training techniques of Dutch ‘Iceman’ Wim Hof, whose ability to adapt to extreme cold has sparked a wave of scienti c interest. Carney also met people who had used cold exposure to lose weight, cure autoimmune diseases and reverse diabetes. Having concluded his own coldweather training with a climb to the snowy peak of Mount Kilimanjaro while wearing nothing but shorts and trainers, he is now convinced that cold exposure is fantastic for the body and mind.

“ere is a moment where the stress is so much that it actually causes damage, so you want to remain in an area where you’re not actually getting, say, frostbite,” warns Carney. “But you do want to be a bit uncomfortable, because it is those sensations of being uncomfortable that are actually the sensations of your body working harder to rise to the challenge.”

FAT THAT MAKES YOU THIN

One of the most interesting areas of research focuses on the cold-induced activation of a substance called ‘brown fat’. Located in your neck, shoulders, chest and back, brown fat has been dubbed ‘the fat that makes you thin’. Whereas normal white fat stores energy from food, brown fat burns energy to produce heat. It has a unique protein within its mitochondria, called uncoupling protein, which, when exposed to the cold, rapidly produces large amounts of heat.

“A gram of brown fat will produce 300 times more heat than a gram of any other tissue in the body when maximally stimulated,” explains Professor Michael Symonds, deputy head of the University of Nottingham’s School of Medicine. “at's quite a phenomenal amount of heat.”

Professor Symonds’ research suggests brown fat could help to prevent weight gain and diabetes. “All the energy for that heat production has got to be drawn from somewhere,” he explains. “And it’s partly from fat in the body, but the other important source is glucose. So potentially it could have a big e ect on glucose metabolism.”

Research suggests that getting even slightly cold boosts non-shivering thermogenesis (NST) – a cold-induced spike in your metabolism – by up to 30 per cent. In one study, when diabetics turned the thermostat down to 15-19°C for a few hours a day, they gained a 43 per cent improvement in insulin sensitivity. “Anything that makes you cold will stimulate your brown fat, and that should be bene cial in terms of keeping your weight down and improving glucose regulation,” says Professor Symonds.

“Getting even slightly cold can spike your metabolism by up to 30 per cent”

COOL RUNNINGS

It seems that regular cold exposure – whether from cold walks or just turning down the thermostat – can unlock remarkable health bene ts. But there are some potential gains from exercising in cold conditions, too.

e usual rules about warming up properly and not getting excessively cold apply. But athletes may be able to perform a better on cold days. Research in the Journal of Applied Physiology suggests cyclists can ride 42 per cent longer in temperatures of 3°C than in toasty 20°C conditions. Data in the International Journal of Sports Medicine revealed that footballers run further at 5°C than at 21°C. And French researchers discovered that marathon runners hit their fastest times when it’s 3.8-9.9°C.

at’s because when we exercise our bodies produce a huge amount of heat – around 20-25 times your resting metabolic heat. So on hot days, your body has to work incredibly hard to keep cool. But on cold days, your body is less stressed, so you have more energy for training. “ere is always an adjustment period to dealing with the cold air in the lungs and potential for injury,” warns Dr Cara Ocobock, director of the Human Energetics Lab at the University of Notre Dame. “But it seems that athletes can push themselves a bit harder in the cold weather because their bodies don’t warm up as much and there is less risk of overheating.”

One activity which this theory doesn’t work for, however, is weight-training, as warm muscles are crucial for optimal explosive performance. “Powerlifters will take longer to warm up than they would in warm weather,” says Dr Ocobock. “is would of course involve some extra warm-up sets and keeping the hands warm, so everything will just take longer, the extra sets can tire the lifter out, and they might not be able to hit their top weight.”

TAKE IT EASY

ere is also a potential complication regarding training intensities. Although the amazing physiological bene ts associated with cold exposure can be easily achieved through simple daily goals like taking cold walks or cold showers, some of the more

speci c cold-exposure adaptations may be switched o if you exercise in the cold at a really high intensity.

“e physical activity will produce heat that will keep you warm,” explains Dr Ocobock. “Human muscle is not 100 per cent e cient and a good deal of energy is dissipated as heat. So this heat will help you maintain core body temperature – despite the cold temperatures.”

So is it better to go for a low-intensity hike or a high-intensity run in the cold?

e simple answer is that it doesn’t matter what you do, so long as you get out there regularly. at’s because there are di erent bene ts to di erent types of cold exposure. Low-intensity jogs, hikes and bikes rides on cool days will crank up your brown fat activity, improve your blood glucose regulation, raise your metabolism and boost your mood. High-intensity runs or bike rides may not trigger all the speci c cold-weather adaptations, but you will instead enjoy an elevation in exercise performance, an improved long-term adaptation to the cold, and a cold-induced endorphin high. And you’re unlikely to stay warm for your whole workout anyway, so you will still bag some of those special cold exposure bene ts, too.

“Every single time you go into a cold environment, you’re sending di erent signals to the unconscious parts of your body to adapt,” concludes Carney. “If it’s the

rst time you’ve done this, it’s going to be uncomfortable. But as you warm up, your metabolism will ramp up and you’ll develop long-term changes that will give you more thermogenic resilience. As the seasons are a natural phenomenon, our bodies are adapted to change. is is exactly what you are built to do.”