Does Your Body Burn More Calories if You Are Hot or if You Are Cold?

Temperature affects how many calories we burn. According to the American Dietetic Association Complete Food and Nutrition Guide, both prolonged exposure to cold temperatures and perspiration to lower body temperature use extra energy. The effect of temperature on your caloric burn rate varies with your body mass and the extremity of the temperature.

How Many Calories You Burn

According to a 2000 study published in Medicine and Science in Sports and Exercise, you can calculate the number of calories you burn if you have a few key pieces of information. Start the equation by multiplying your body weight in kilograms by 3.5. Multiply the product of this equation by a metabolic equivalent intensity level, or MET. Then divide the entire product by 200. MET is a value that represents the calorie-burning potential of an activity. Walking has a MET of 2.5. Bodily function with no additional activity is assigned a MET of 1. This is known as your basal metabolic rate, or BMR. The equation to figure your BMR can be expressed as: (MET x body weight in kg. x 3.5)/200 = calories burned per minute. If you weigh 220 lbs., which is about 100 kg, you burn around 1.75 calories per minute or 105 calories per hour.

Effects of Temperature on BMR

According to the text, "Thermal Effects on Cells and Tissues," BMR changes as a function of temperature. BMR will change by seven percent for each temperature change of 0.9 degrees Fahrenheit. Thus, when external conditions affect your body temperature, your body will burn more calories as it tries to compensate for the anomaly and restore your body to its normal temperature, increasing your BMR. This effect occurs in conditions of both heat and cold.

Heat and BMR

Your BMR reacts more slowly to external heat than it does cold. Short exposures to higher temperatures have little effect on your BMR. The text, "Basics of Clinical Nutrition," notes that your body's mechanisms to increase heat loss, such as perspiration, adjust for temperature increases and mitigate their effects on BMR. Prolonged heat exposure or an increase in internal temperature, however, can raise your BMR. For example, if you have a fever that is 3 degrees Fahrenheit above normal, your BMR will increase more than 20 percent.

Cold and BMR

Your body responds quickly to heat loss that arises from cold external temperatures. Your muscles move and twitch; you shiver, which increases your bodies heat production by as much as five times its normal level, according to Suzanne Schneider, a professor in the Department of Physical Performance and Development at the University of New Mexico. Your body constricts veins and re-routes blood flow initially, toward the skin and then back toward your core as internal temperature decreases, increasing your overall BMR.

Heat vs. Cold

The answer to whether your body uses more calories if you are hot or if your are cold is: it depends. If you walk outside in cold weather, your body will immediately raise its BMR to compensate for heat loss and burn more calories. You will burn few extra calories in hotter weather unless you are exposed for a long period of time. On the other hand, if your internal temperature increases a few degrees, your BMR begins to rise quickly. A fever of 105 F, for example, represents an almost 50 percent increase in BMR. Burning calories at this rate can lead to tissue damage and threaten your life.