As the temperature drops over the winter months, the temptation is always there to stay snug indoors by the fire – or even the radiator – rather than making the effort to get outside. If you do so, however, you may be missing out on a key way to boost your health without putting in any extra effort.
Exercising in the cold has been shown to stimulate the creation and activity of our body’s brown adipose tissue, which is also known as brown fat. This type of fat is interesting because unlike white fat, which handles energy storage, it is involved in heat production and energy expenditure. So as brown fat burns calories to generate heat, it can burn off your excess white fat. Some doctors even call it good fat.
"Being active outside has many benefits such as breathing fresh air, accessing green space . . . and exposure to a greater depth of visual field, which can help eyesight," says Dr Grace O'Malley, a research lecturer and chartered physiotherapist at Royal College of Surgeons in Ireland, and a former chairwoman of the Association for the Study of Obesity on the Island of Ireland.
“Also, some research suggests that being active in cooler environments can help boost metabolism via the body’s natural processes of thermoregulation – our body has ways to maintain core body temperature so that essential functions are not compromised.”
We are not talking here about the practice of jumping into an ice bath after an extreme workout, as tennis player Andy Murray, Olympian Mo Farah and many footballers have done in the name of boosting their recovery. As well as being uncomfortable, that may not even be worthwhile. A study conducted by the Queensland University of Technology last year indicates that the practice may be no more effective than doing a low-intensity warm down.
The cool of an Irish winter's day is enough to make a difference. Research by the late endocrinologist Dr Paul Lee from Sydney's Garvan Institute of Medical Research conducted in 2014 shows that spending just six hours a day in an environment of 19 degrees over a month can make a difference.
“The big unknown until this study was whether or not we could actually manipulate brown fat to grow and shrink in a human being,” Dr Lee said at the time. “What we found was that the cold month increased brown fat by around 30-40 per cent.”
While a cool environment stimulated the growth of brown fat cells, a warm environment caused a loss. Once the regular temperature was set at 24 degrees, which is about the level needed to wear a T-shirt indoors in winter, the level of brown fat in the subjects dropped back, returning to baseline. He also conducted studies that showed in the laboratory that our white fat cells can change into brown fat cells.
Babies have a lot of brown fat, but until recently it was believed that adults did not. In 2009, however, researchers at the University of Maastricht showed that brown fat can be activated by cold exposure. It was also shown that those who are overweight have little or no brown fat.
This is a developing area of research. Earlier this year, researchers at the Technical University of Munich discovered that we have three times more brown fat than previously believed. The study was published in the Journal of Nuclear Medicine. It seems that those with plenty of brown fat tend to be lean and have better blood sugar levels.
Some scientists hope to develop drugs to activate brown fat to help those with diabetes. In the meantime, however, there are habits you can adopt that will not have the side effects a drug might.
Chief among these is turning down the thermostat at home or at work. “We rely too much on a heated environment and expect to be able to go around wearing T-shirts indoors in winter,” says Dr O’Malley. “Of course you don’t want to be shivering at home, but just think twice about whether the heat should go on or whether moving around the house and getting some jobs done would be another option.”
By not turning up the heat, you will enhance your body’s ability to regulate your temperature naturally. “It can motivate people to move more if it is slightly on the chilly side,” says Dr O’Malley. “The body naturally reacts to cold by moving in order to heat itself up.”
Take it outside to get the full effect but do take care. You don't need to take off your clothes and expose yourself to extreme temperatures, as does Wim Hof, a Dutchman also known as "the Iceman" thanks to his ability to withstand extreme cold, which he attributes to meditation, a special breathing technique and exposure to cold.
When exercising in cold weather there are a few considerations: cold air may trigger bronchoconstriction – narrowing of the airways – so those with asthma should be prepared with their inhaler, or try to breathe through the nose so that air can be warmed and moistened. Your GP can advise on specifics if you have asthma, cardiac or other breathing conditions.
It’s important to warm up so as to avoid injury and to do a slightly extended cool down.
Ignore the Iceman and dress appropriately. Wear layers of clothes that you can take off and put back on after exercise. So after sweating, you don’t get too cold. Also wear a base layer to remove moisture from the skin and be sure to protect extremities.
“Our weather is fairly moderate but if the temperature really drops it’s important to know the signs of cold injury and frostbite,” said Dr O’Malley. “Don’t forget to hydrate, which we can tend to forget about in cooler weather.”
Avoid extreme cold and if there is ice on the ground you may need to rethink the type of exercise you are doing in order to avoid slips and falls. Then get a warm glow thinking of all those lovely brown fat cells you are waking up and putting to work.
How to make your brown fat work for you
- Turn down the thermostat at home or in the office
- Go outside when it is cold
- Let your body warm up naturally