WINTER NUTRITION: Fueling for Cold Weather Exercise

author : Nancy Clark

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Lack of food and fluids can take the fun out of your outdoor activities. These tips can help you fuel wisely for cold weather workouts.

If you are a winter athlete, you want to pay careful attention to your sports diet. Otherwise, lack of food and fluids can take the fun out of your outdoor activities. These tips can help you fuel wisely for cold weather workouts.

Winter hydration

Failing to drink enough fluids is a major mistake made by winter athletes. A study comparing hydration status of athletes who skied or played football or soccer, reported the skiers had the highest rate of chronic dehydration. Before a competition, 11 of the 12 alpine skiers showed up dehydrated. (1).
 
• Some winter athletes purposefully skimp on fluids to minimize the need to urinate. There's no doubt that undoing layer after layer of clothing (ski suit, hockey gear, etc.) can be a hassle. Yet, dehydration hurts performance and is one cause of failed mountaineering adventures.
 
• Cold blunts the thirst mechanism; you'll feel less thirsty despite significant sweat loss and may not “think to drink.”
 
• Winter athletes (especially those skiing at high altitude) need to consciously consume fluids to replace the water vapor that gets exhaled 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. You can see this vapor (“steam”) when you breathe.
 
•  Unless you are hot, you do not want to drink icy water (i.e., from a water bottle kept on your bike or outside pocket of your back pack). Cold water can cool you off and give you the chills. The better bet is having an insulated water bottle or a bottle filled with hot sports drink then covered with a wool sock to help retain the heat.
 
• Dress in layers, so you sweat less. Sweaty clothing drains body heat. As the weather becomes “tropical” inside your exercise outfit, make the effort to strip down. You’ll stay drier and warmer.  Simply taking off a hat is cooling; 30% to 40% of body heat gets lost through the head.

Winter fuel

You need adequate pre-exercise fuel to generate body heat. Hence, you want to fuel-up before you embark on winter exercise, particularly before you ski, run outside, or embark on any outside activity in extreme cold.
 
• 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. Hence, eating not only provides fuel but also increases heat production (warmth).
 
• Aerobic workout can increase your metabolism by 7 to 10 times above the resting level. That means, if you were to exercise hard for an hour and dissipate no heat, you could 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. Exercise is an excellent way to warm up in the winter!
 
• If you become chilled during winter exercise (or even when swimming, for that matter), you'll likely find yourself searching for food. A drop in body temperature stimulates the appetite and you experience hunger. Your body wants fuel to "stoke the furnace" so it can generate heat. 
 
• For safety sake, you should always carry some source of emergency food (such as an energy bar) with you in case you slip on the ice or experience some incident that leaves you static in a frigid environment. Winter campers, for example, commonly keep a supply of dried fruit, chocolate, or cookies within reach, in case they wake up cold at 3:00 a.m..

Energy needs
 
Cold weather itself does not increase energy needs, but you will burn extra calories if your body temperature drops and you start to shiver. Shivering is involuntary muscle tensing that generates heat.
 
--When you first become slightly chilled (such as when watching a football game), you'll find yourself doing an isometric type of muscle tensing that can increase your metabolic rate two to four times.
 
--As you get further chilled, you'll 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'll be glad you have emergency food with you!
 
• Your body uses 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 skiing for an hour in 0° F weather, you might use about 150 of those calories to warm the inspired air.  In summer, you would have dissipated that heat via sweat.
 
• If you wear heavy clothes, you will burn a few more calories carrying the extra weight of skis, boots, heavy parka, snow shoes, etc.. The Army allows 10% more calories for heavily clad troops who exercise in the cold. If you are a runner, however, the weight of your extra clothing is minimal. Think twice before chowing down!

Winter recovery foods
 
• To chase away chills, replenish depleted glycogen stores, and rehydrate your body, enjoy warm carbohydrates with a little protein, such as hot cocoa made with milk, oatmeal with nuts, lentil soup, chili, and pasta with meatballs. The warm food, added to the thermogenic effect of eating, contributes to rapid recovery.
 
• In comparison, eating cold foods and frozen fluids can chill your body. That is, save the slushie (ice slurry) for summer workouts; it will cool you off. In winter, you want warm foods to fuel your workouts. Bring out the mulled cider or thermos of soup!

Winter weight gain

Many athletes bemoan winter weight gain. Some eat too much because they are bored and less active. Others experience seasonal affective disorder (SAD) and the change of seasons has a marked affect upon their mood. Changes in brain chemicals increase carbohydrate cravings and the desire to eat more. The temptations of winter holiday foods can also contribute to weight gain. 

• To limit winter weight gain, stay active! Exercise helps manage health, weight, and the winter blues. The tricks are to invest in proper clothing, fuel well, and prevent dehydration so you can stay warm and enjoy winter’s outdoor wonderland.
 
Nancy Clark, MS RD offers nutrition consultations to casual exercisers and competitive athletes at her private practice located at Healthworks, the premier fitness center in Chestnut Hill MA (617-795-1875). Her popular Sports Nutrition Guidebook and food guides for runners, cyclists, and soccer players are available at http://www.nancyclarkrd.com/. See also http://www.sportsnutritionworkshop.com/.

Reference
1. Johnson C, A Davenport, M Hansen, D Bacharach. Pre-competition hydration status of high school athletes participating in different sports. Med Sci Sport Exerc 42(5): S128 (Abstract 1149).

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date: December 22, 2011