Training Outside in the Winter? Be Sure to Fuel Correctly

It’s important to tweak your nutrition to keep your training in full gear as temperatures plunge. Here's how to fuel in cold-weather conditions.

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For those who like to train outdoors throughout the winter months, we salute you. From slippery sleet to skin-peeling wind chill, there’s seemingly nothing that can keep you inside. But if you’re brave enough to face the cold, then you need to understand how to properly adjust your fueling for your wintry outdoor pursuits.

The season of layers can be a time to make a few important tweaks to your sports nutrition habits. That’s because exercising in cold temperatures presents some unique nutrition and hydration challenges you’re not faced with during the summer months. Make a few missteps and it could suck all the remaining warmth out of your winter training.

Here’s everything you need to know to stay comfortable and safe while still performing at an optimal level—even when the weather outside is frightful.

RELATED: Triathlete’s Complete Guide to Nutrition and Fueling

You may be hungrier than usual

While you may run or ride the same route in warmer months without the urge to reach for the feed bag, that may not be the case during the deep freeze. In cold weather, it’s normal for your body temperature to drop, which can stimulate appetite and drive up feelings of hunger. Hence, if you become chilled during winter exercise you’ll likely find yourself searching for calories. You should permit yourself to eat—and, better yet, not get hungry in the first place.

Hunger pangs can increase the perception of effort, which may cause you to scale down the pace or prematurely call it quits. Also, eating stokes the furnace, generating heat and helping warm your body a degree or two. Food’s overall warming effect is known as thermogenesis. Your body generates more heat when in a fed state than when you have an empty stomach. Think about that flushed feeling you have after polishing off a huge meal.

So eating not only provides fuel but also increases heat production (warmth). That means you should never let yourself get too “low” during exercise in the cold or you risk succumbing to hunger and a case of shivers.

Fuel any outdoor workout lasting more than an hour

There isn’t much in the way of research regarding the impact that working out in chilly climates has on fuel stores. But we do know that your body is going to allow some additional energy above what is needed for muscular contraction for preserving body temperature and to warm and humidify the air you breathe when you exercise in the cold. These processes can be considered non-shivering thermogenesis and may necessitate the need to consume calories to compensate for. If you do end up getting really cold, research demonstrates that muscle glycogen is a primary fuel source to generate the heat needed in the body to combat any shivering that occurs. (Shivering is involuntary muscle tensing that generates heat.) So even if exercising at lower intensities, the onset of shivering can drain this vital energy source as the body further ramps up thermogenesis. It’s important to keep in mind that prolonged exhaustive exercise can itself lead to glycogen depletion which, in turn, could compromise your ability to maintain proper thermal balance and making it harder to continue your workout and raising the risk for hypothermia. Also, if you are wearing a lot of winter gear, you will burn a few more calories to carry the extra weight of layers of clothes, and any gear such as skis.

Athletes who are not acclimated to exercising in the cold will likely tap into their glycogen stores to stay warm even more so than cold-hearty athletes. So an Alaskan triathlete will be more fuel-efficient (i.e. burning more fat, fewer carbs at a given work rate) during cold-weather workouts than a counterpart from Arizona.

What this means is that for cold weather exercising lasting longer than an hour or so it is important to fuel yourself. This is due to food being used to fuel the body’s increased metabolic needs in addition to providing energy for the exercise itself. You want to eat continually to replace carbohydrate stores that are being used for exercise and warming. If you don’t replace this energy you will likely feel more fatigued than you would like and could become uncomfortably chilled. Plan to fuel yourself with 100-200 calories, 30 to 60 grams of carbs for every 30 to 45 minutes of activity. This can come from the usual suspects like gels, chews, bars and sports drinks. Of course, it’s important to make sure that any fuel you bring along doesn’t freeze solid. Biting into an energy bar brick will not only greatly lower the chances you’ll eat as much as you need, it can land you in the dentist’s chair. Keeping your food insulated in a hydration pack can help prevent it from freezing as can storing it in the pocket of a layer of clothing that is close to your body.

And finally, winter athletes should carry an emergency food source, just in case some incident leaves you static in a cold setting. The extra food can help keep you warm.

RELATED: What to Wear for Bike Rides, by Temperature

Don’t forget to drink up

One thing most exercisers neglect in the winter is proper hydration, but it’s not your fault—your brain’s ability to detect thirst is compromised in the cold. This might be the result of less sodium loss through sweat than what occurs when working out in a hot environment. That means an athlete needs to make a more conscious effort to consume enough fluids to maintain a better hydration balance.

Although your fluid requirements in winter aren’t as high as in the middle of summer when you’re sweating buckets, that doesn’t mean you can or should ignore your hydration needs when training alongside Jack Frost. You lose fluids just by breathing in the cold air because your body adds humidity (i.e. moisture or condensation) to warm the air in your lungs. You can see this vapor (“steam”) when you breathe. When we exhale at a faster rate during exercise, a significant amount of water is lost into the air. Add this to the perspiration that can still occur during cold exercise, especially if you are overdressed, and you can end up dehydrated, which will put a ding in your training pace or ability to continue with exercise. We may not realize how much we’re sweating in the winter as the additional clothing absorbs much of our sweat. It does appear, however, that being in a hypohydrated state in cold environments does not negatively impact performance to the same degree or place as much of a strain on the body as it does during hot, humid climates.

There is no reason to drink gallons of fluid, but do your best to take in about 4 ounces of fluid for every 15 minutes of activity, especially if exercise duration is longer than 60 minutes. Since it’s not advisable to drink to thirst when your thirst mechanism is compromised in the cold, set your watch to beep every 15 minutes as a reminder. Sodium losses will be less than when working out in steamy conditions, but it’s still a good idea to include some in your hydration efforts if you are training for a long period of time to make sure levels don’t dip too low. Aiming for anywhere from 300 to 600 milligrams for each hour of activity should suffice. Several sports drinks formulations can help you get this amount.

RELATED: Are You Doing Thirst Right? The Science Says Probably Not

Turn up the heat on your hydration

When it comes to drinking during cold-weather exercise, warmer fluids are ideal. The problem with cold water is that it can start to chill the body thus requiring the use of more energy to stay warm. In summer, this cooling effect is helpful during exercise, but not so much when the snow is flying.

Athletes who aren’t opposed to training in the great outdoors when temps have plunged have all sorts of hacks for preventing their fluid from turning into an icy slurry. Wearing a hydration pack can help keep your water close to your body and warmer than if it is carried in an external water bottle. You can also try covering a water bottle filled with warm liquid with a wool sock or a neoprene insulating sleeve. The wider the mouth of your water bottle, the longer it will take for water to completely freeze over your bottle’s opening. Or make use of an insulated water bottle—just be sure not to fill it with boiling water, as it will remain too hot to safely drink when pushing the pace. Skratch Labs Hot Apple Cider Hydration Drink Mix  provides easily digested carbs and electrolytes and is designed to be served warm to help you feel all cozy inside when training hard.

Recover with comfort foods and drinks

The best way to warm yourself up while simultaneously kick-starting recovery is to start refueling and rehydrating on hot carbs. Hot cider, hot chocolate, steaming soup, as well as oatmeal or even chili will all work. The warm food, added with the thermogenic effect of eating, contributes to body temperature recovery.

This recovery nutrition should include both carbohydrates and protein. The purpose of the carbs at this time is to replace the muscle fuel (glycogen) utilized during the chilly workout. The protein will help stimulate the development of new muscle tissue and also raise insulin levels to help drive more recovery nutrients into your muscles. So hot chocolate made with milk and some sweetener will deliver both carbs and protein. As will a hearty bowl of chili containing sweet potato and chunks of meat. A steamy bowl of oatmeal with some protein powder mixed in is another example of this dynamic duo that can warm you up from the inside.

RELATED: 4 Ideas for Hearty Recovery Meals

Don’t skimp on calories

There is a reason why polar explorers aim to pack on the pounds before their expeditions—extra insulation helps keep their bodies warmer when physically exerting themselves in a frigid environment. While you certainly shouldn’t stuff your silly to the point where you are greatly tipping the scale, off-season training in the cold is not the best time to lose significant body weight through inadequate fueling.

When heavy physical activity is coupled with chronic underfeeding, the resulting negative energy balance is likely to lead to loss of body mass, and the corresponding reduction in tissue insulation, in turn, compromises thermal balance by facilitating conductive transfer of body heat from the core to shell. The upshot is that negative energy balance through underfeeding can affect thermoregulation during cold exposure thereby impacting performance and also raising the risk for hypothermia.

This means for improved heat conservation and to better defend body temperature it’s important to couple your training with calorie consumption.

Also, under-fueling will also likely result in subpar glycogen stores, which could impact performance since training in the cold can place added stress on this vital energy reserve. This will be particularly detrimental if you’re training at higher intensities that call upon a greater use of glycogen for energy generation.

RELATED: RED-S Is Still A Major Problem in Endurance Sports

Up your iron intake

If you’re someone who has a hard time staying warm during your winter outings, there is a chance that low iron levels could be part of the problem. A little-known side-effect of chronic iron deficiency is that it can impair your ability to maintain adequate body temperature by impacting thyroid functioning, which hinders heat production within the body. There is data to suggest the rates of iron deficiency are increasing in America owing to inadequate intakes. This investigation in the Clinical Journal of Sports Medicine determined that both male and female runners are at risk for iron deficiency and anemia, with higher rates appearing in elite triathletes and runners.

If you suspect you might be operating on inadequate iron levels, have your physician perform a blood test and, if necessary, take the necessary dietary measures such as those outlined here to get your levels up to where they can overturn a deficiency and help keep you feeling toasty while braving the wind chill.

Matthew Kadey, M.S., R.D., is an author and journalist who specializes in sports nutrition and is the recipient of the 2013 James Beard Award for Food Journalism.