Several different factors affect metabolism, or how many calories your body burns each day. You may have heard that your core body temperature can increase or decrease your metabolism. This appears to be true -- and outside air temperature may also affect how many calories your body burns daily.
High Body Temperatures
Research shows that higher core body temperatures appear to increase metabolism. A review published in 2009 in Transactions of the American Clinical and Climatological Association reports that an increase in body temperature is associated with a higher metabolic rate, and higher body temperatures do speed up metabolism. Authors of this review suggest that for each degree Celsius your body temperature rises, your metabolism increases by 10 to 13 percent -- which means you'd expend an extra 100 to 130 calories per day if you normally eat 2,000 calories daily because body temperature accounts for 50 percent of your energy expenditure.
Cooler Body Temps
Cooler core body temperatures appear to lower metabolic rates. The review published in 2009 in Transactions of the American Clinical and Climatological Association notes that a 1 degree Celsius drop in body temperature decreases metabolism and causes you to expend about 100 to 130 fewer calories each day.
Does Outside Air Temperature Matter?
While a warmer body temperature does tend to increase metabolism, cooler air temperatures may also boost metabolism. According to the National Institutes of Health, men exposed to cooler air temperatures showed increases in brown body fat and higher metabolisms in a 2014 study published in Diabetes. A study published in 2014 in Plos One also found that energy expenditure is higher during exposure to cold temperatures, and cold exposure significantly increases metabolism in mice.
What about Exercise?
Exercise causes an elevation in body temperature and an increased metabolism during physical activity. In fact, muscle has a higher metabolic rate than body fat, so the more muscle mass you gain by exercising, the higher your metabolism will be, even during periods of rest. Exercising in hot weather burns more calories than working out in cold temperatures because it takes more energy to cool your body in the heat, reports the American Council on Exercise (ACE). An exception is if you're shivering. ACE notes that shivering can cause you to expend 400 calories in just one hour.
An experienced health, nutrition and fitness writer, Erin Coleman is a registered and licensed dietitian and holds a dietetics degree from the University of Wisconsin-Madison. She also has worked as a clinical dietitian and health educator in outpatient settings. Erin's work is published on popular health websites, such as TheNest.com and JillianMichaels.com.