There’s something about plowing powder all day that makes you think: I’ve definitely earned fondue tonight. Winter weather has the effect of making you crave hearty winter fare. But do sub-zero workouts really create a bigger calorie deficit?
The answer is only in very specific scenarios, says Bob Seebohar, a registered dietitian, coach and exercise physiologist. “Energy expenditure will increase only if it is cold enough to induce the shivering response, [which is] usually below 32 degrees.”
If you do end up shivering, your calorie burn will go through the roof. Seebohar says that shivering can double, triple, or maybe even quintuple your metabolic output. And a 2010 review of studies on shivering, published in Frontiers in Bioscience, found that 75-to-80 percent of the calories consumed by shivering came from muscle glycogen stores. So if you find your teeth chattering, you’ll want to increase your carb load.
Sadly, if you’re properly dressed for the weather, you probably won’t shiver and therefore won’t need to ingest extra fuel. “This doesn't mean you should intentionally underdress in the cold for a greater increase in calorie expenditure,” warns Marni Sumbal, a board-certified sports dietician and triathlon coach. Doing so just increases your risk for frostbite. A good alternative is simply to put on a coat and do a few extra intervals instead.
The other way that working out in the cold could help you burn more calories is through the activation of brown fat. Brown adipose tissue (or brown fat) helps us regulate our body temperatures by burning calories. Babies are born with a fair amount of the stuff, but until recently, researchers thought we lost it all as we matured. It turns out that’s not the case. Adults can retain a small amount, under the right circumstances.
“One of the most powerful ways to activate brown fat is exercising in cold temperatures. Thus, skiing or cross-country skiing will be very good to activate brown fat,” says George King, chief scientific officer at Joslin Diabetes Center, as well as a professor of medicine at Harvard Medical School. Another great way to activate brown fat is through regular exercise. The Joslin Diabetes Center recently introduced a special workout, called the “Joslin Coolout” that uses cool temperatures to specifically activate brown fat—but you could also just go run outside on a chilly day. Best of all, King says that it doesn’t really need to be that cold to get your brown fat going. “Temperatures around 62 degrees Fahrenheit will be enough to activate brown fat.”
Still, brown fat activation won’t earn you a hot fudge sundae. According to King, at most, brown fat can only burn between 100 and 300 extra calories a day.
With this in mind, here are some important things to keep in mind when working out in the winter:
Don’t Forget to Hydrate
“The body is producing a great deal of heat, especially in temperatures below 32 degrees, thus the sweat response will still be high,” Seebohar says.
Furthermore, “Breathing in cold, dry air causes a significant loss of water in order to warm and humidify the air which then is lost with each exhalation,” says Richard Quincy, the former medical director for the U.S. Ski and Snowboard Association. “Winter athletes therefore have a need to replace the water that is lost by respiration as well [as sweat]. Since the thirst mechanism is reduced in cold weather, there is a decreased desire to drink fluids so a conscious effort for fluid hydration is essential.”
Keep Your Fuel from Freezing
Of course, there’s always the age-old problem of keeping your fluids and foods from freezing. “Spend a couple of hours riding in -10 degrees and biting into a PowerBar is like biting into a granite countertop,” says Patrick Sweeney, a professional adventure athlete who has traversed the Arctic Circle and the Iditarod route via fat bike and was the first to pedal to Everest Base Camp. “I’ve actually stuck things down my cycling shorts to get them to the point where I could eat them,” he says.
To get winter fueling right, choose things that are still edible when frozen, or that will thaw quickly. Keep your water close to your skin if possible; Sweeney packs his hydration bladder against his body and is careful to blow back into the bladder after every sip. His two current favorite non-freezing foods are chocolate fudge made with coconut oil (which becomes liquid at a very low temperature), and thick cut bacon coated with brown sugar. “It’s almost a taffy-like consistency when it’s frozen,” he says.
Sweeney may be onto something with his solid food standbys. “As long as intensity isn't high, there will be blood flow to the gut to help with digestion so many athletes prefer solid foods in the winter instead of sport drinks, gels, blocks, etc.,” says Sumbal. “In hot weather, that blood is diverted to the skin for cooling which is why many athletes experience GI issues when trying to fuel with concentrated food sources in the heat.”