If you are a human in winter today, take solace in the knowledge that being outside burns calories. In the journal Trends in Endocrinology and Metabolism, scientists from Maastricht University in The Netherlands argue that when exercise isn't an option, "regular exposure to mild cold may provide a healthy and sustainable alternative strategy for increasing energy expenditure."
Shivering can increase your metabolic rate as much as five fold. The problem with shivering is that it is terrible, so Dr. Wouter van Marken Lichtenbelt and colleagues looked into being only mildly cold as a way to burn calories. Our bodies burn energy to keep us warm in a process called non-shivering thermogenesis (NST), they explain, which works even at pretty reasonable temperatures. They defined mild cold exposure as 64 degrees Fahrenheit.
"In most young and middle-aged people NST increases by between a few percent and 30 percent in response to mild cold exposure," they write. They say that can significantly improve your calorie-in to calorie-burned ratio. Even if you eat more to compensate, most people won't eat enough to undo the extra expenditure.
"Indoor temperature in most buildings is regulated to minimize the percentage of people dissatisfied," they note, apparently in reference to some ideal world that is not our office. "By lack of exposure to a varied ambient temperature, whole populations may be prone to develop diseases like obesity. In addition, people become vulnerable to sudden changes in ambient temperature."
This idea is like a Paleo Diet for your surroundings. Our bodies aren't meant to always be in ideally temperate environments. Letting the temperature of your home or office vary significantly with the seasons is good for you and the environment.
"Cold exposure alone will not save the world," they write, "but it is a serious factor to consider in creating a sustainable environment together with a healthy lifestyle."
A 2013 research article in Cell Metabolism did suggest that, in mice at least, cold exposure could increase one's risk for cardiovascular disease. Earlier this month in the very same journal, though, researchers from the National Institutes of Health said that the effects of shivering and exercise are very similar, and the endocrine changes in our bodies in response to cold are "exploitable in obesity therapeutics development." Being cold activates brown fat, they observed, which burns calories rapidly to generate heat. Dr. Francesco Celi, a professor at Virginia Commonwealth University who oversaw those experiments, told The New York Times that if you can’t get to the gym, consider lingering outside at the bus stop.
I don't see why it should be a bus stop. On frigid days like this one, the inside of most bars count as mildly cold.
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