Some athletes embrace winter's chill as a welcome change from running in summer's heat. But others complain about hating cold weather. If that is your stance, remember that exercising with proper nutrition (and layers of dry clothing) offers the opportunity to chase away the chills. After all, an aerobic workout can increase your metabolism by 7 to 10 times above the resting level. This means, if you were to exercise hard for an hour and dissipate no heat, you could raise your body temperature from 98.6 to 140 degrees °F. (You'd cook yourself in the process!). In the summer, your body sweats heavily to dissipate this heat, but in the winter, the warmth helps you survive in a cold environment. Runners can enjoy a tropical environment in their running suit within minutes of starting exercise.
Because food provides the fuel needed to generate this heat, the right sports diet is particularly important for runners and other athletes who are exposed to extreme cold, such as skiers and skaters. Here we address some common questions and concerns about winter and nutrition and offer tips to help you enjoy the season. For safety sake, winter athletes should always carry with them some source of fuel in case of an unexpected slip on the ice or other incident that leaves them static in a frigid environment. Winter campers, for example, commonly keep a supply of dried fruit, chocolate or cookies near by for fuel if they wake up cold in the middle of the night. You want to have an emergency energy bar tucked in your pocket, just in case...
Why do we feel hungrier in the winter than in the summer? A drop in body temperature stimulates the appetite and you experience hunger. Hence, if you become chilled during winter exercise (or when swimming, for that matter), you will likely find yourself searching for food. Eating "stokes the furnace", generates heat, and helps warm your body. Food's overall warming effect is known as thermogenesis (that is, "heat making"). Thirty to sixty minutes after you eat, your body generates about 10% more heat than when you have an empty stomach. This increased metabolism stems primarily from energy released during digestion. Hence, eating not only provides fuel but also increases heat production, warmth.
Do we burn more calories when we exercise in the cold? Cold weather itself does not increase calorie needs. You don't burn extra calories unless your body temperature drops and you start to shiver. (And remember: the weather can actually be tropical inside your exercise outfit). Your body does use a considerable amount of energy to warm and humidify the air you breathe when you exercise in the cold. For example, if you were to burn 600 calories while cross-country running for an hour in 0 degrees °F weather, you may use about 23 percent of those calories to warm the inspired air. In summer, you would have dissipated this heat via sweat. In winter, you sweat less. If you are wearing heavy clothes, you will burn a few more calories to carry the extra weight of skis, boots, heavy parka, snow shoes. The Army allows 10% more calories for the heavily clad troops who exercise in the cold. But the weight of extra clothing on, let's say, winter runners is generally minimal.
Why do we shiver when we get cold? Shivering is involuntary muscle tensing that generates heat and offers a warming effect. When you first become slightly chilled (such as when watching a football game), you will find youself doing an isometric type of muscle tensing that can increase your metabolic rate two to four times. As you get further chilled, you will find yourself hopping from foot to foot and jumping around. This is Nature's way to get you to generate heat and warm your body. If you become so cold that you start to shiver, these vigorous muscular contractions generate lots of heat - perhaps 400 calories per hour. Such intense shivering quickly depletes your muscle glycogen stores and drains your energy. This is when you will be glad you have some emergency food in your pocket!
What is a big nutritional mistake made by winter athletes? Failing to drink enough fluids is a major problem among winter athletes - runners and winter hikers alike. Cold blunts the thirst mechanism; you will feel less thirsty despite significant sweat loss (if you overdress), to say nothing of respiratory fluid loss. That is, winter athletes need to consciously consume fluids to replace the water that gets lost via breathing. When you breath in cold dry air, your body warms and humidifies that air. As you exhale, you lose significant amounts of water. Some winter athletes purposefully skimp on fluids because urinating can be problematic - too much hassle to shed layers of clothing. Yet, dehydration hurts performance and is one cause of failed mountaineering adventures.
What's best to eat to warm up? If you become chilled by the winter weather, as can easily happen if you wear sweaty, wet clothing that drains body heat, fail to wear a hat (30 to 40% of body heat can get lost through the head), or drink icy water (from a water bottle kept on the outside pocket of your backpack when winter hiking), the best way to warm yourself up is to consume warm carbohydrates - hot cocoa, mulled cider, and steaming soup, as well as oatmeal, chili, and pasta. The warm food, added to the thermogenic effect of eating, contributes to rapid recovery. In comparison, cold foods and fluids chill your body. Research subjects who ate a big bowl of ice cream in five minutes experienced a drop in fingertip temperature of 2 degrees °F in the first five minutes, 5 degrees in 15 minutes. In summer, this cooling effect is desirable, but in winter, hot foods are the better way to warm yourself. Bring out the thermos of soup!
Why do we gain weight in the winter? Some people eat more because they are bored and less active. Instead of going out running, they are eating mindlessly in front of the television. For others, the change of seasons has a marked affect upon their mood (known as Seasonal Affective Disorder). Changes in brain chemicals increase carbohydrate cravings and the desire to eat more. Holiday temptations also contribute to weight gain. A study of 195 people indicates they gained on average 0.8 pounds in the six weeks between Thanksgiving and New Years. Overweight and obese people gained even more, with about 14% of the group gaining more than five pounds. The problem is, very few of the subjects lost those holiday pounds... that is eight pounds in ten years. One weight management solution is to stay active in the winter. By investing in proper clothing, you will be able to stay warm from head to toe. You will benefit from not only being able to enjoy exercise but also from sunlight - a good way to battle winter depression (and attempts to cheer yourself up with food). Winter exercise is an asset for managing health, weight and the winter blues. The tricks are to dress right, fuel well, prevent dehydration - and you'll stay warm!
Run The Planet thanks Nancy Clark for the permission to reprint the article "Winter and Nutrition: Fueling for cold weather exercise" by Nancy Clark. Text © by Nancy Clark. Nancy Clark, MS, RD, is the Director of Nutrition Services, SportsMedicine Associates and author of "Nancy Clark's Sports Nutrition Guidebook" and "Nancy Clark's Food Guide for Marathoners: Tips for Everyday Champions". She offers nutrition consultations to casual exercisers and competitive athletes at her private practice located at Healthworks, the premier fitness center in Chestnut Hill (Usa/Massachusetts). Books and sports nutrition teaching materials are available at www.nancyclarkrd.com. Illustration © 2004 by Run The Planet.