12 Ways Your Body Changes in Winter to Stay Warm

If you've lived anywhere with cold, wet winters, you've certainly noticed how the weather affects your body. Those plummeting temperatures can mean dry skin, itchy eyes, and a bummer mood. It's not all bad, though: Without you even realizing it, your body is working behind-the-scenes to make sure you're not too chilly. Here are 12 of the most amazing ways your body changes in the winter to keep you warm.

There's a lot going on under the surface when cold weather hits. As temperatures outside drop, "the body increases blood flow to the skin," says Thomas L. Horowitz, DO, of CHA Hollywood Presbyterian Medical Center in Los Angeles. "It opens the blood vessels to bring warm blood to areas that are cold."

Sorry if you're squeamish, but it's all about the blood. Lower temperatures cause your blood vessels to narrow, which the Mayo Clinic points out increases your blood pressure, since more pressure is required to push blood through your constricted veins and arteries.

The tightening of your blood vessels happens because "your body tries to keep warm blood close to the internal organs," says Seth Newton, PhD, the founder of OutMore. But after your blood vessels constrict, they dilate—and that causes a reaction you've probably noticed. "Your skin gets a rush of blood which can cause a pink hue on the skin, especially on your nose and cheeks," Newton adds.ae0fcc31ae342fd3a1346ebb1f342fcb

Interestingly enough, when you spend more time in cold weather, your body gets used to it and becomes more efficient at cycling between blood vessel constriction and dilation. As a result, the cold weather feels less severe. According to Newton, it takes your body about four weeks to adapt to cold climates.

If you've ever noticed that you have to pee when you're out in the cold, it's not your imagination. It's all connected, as Rick Curtis, director of Princeton University's Outdoor Action Program, explains. Your veins tighten, there's increased pressure in your blood stream, and the kidneys draw out more fluid to reduce that pressure. Also, Curtis says, "A full bladder is a place for additional heat loss, so urinating will help conserve heat."

If you've ever been really cold, you probably started shivering. Horowitz explains that this happens for a good reason: The muscle activity from shivering helps generate heat to keep you warm.

"Shivering is a rhythmic contraction of skeletal muscles," Snehalata Topgi, MD, a doctor with Paradocs Worldwide, adds. "Think about it as your muscles doing sit-ups and creating a warm environment."

Take a look at your arm when you walk into a cold room or feel a chilly breeze outside, and you'll probably notice some goosebumps. Though they may look funny, goosebumps used to serve a very real purpose, according to the Smithsonian National Museum of Natural History. The muscles around our hair follicles contract because, for our much hairier ancestors, that meant additional protection from the weather. But for modern humans—who have significantly less body hair—goosebumps are really just aesthetic.

Though you may have heard that we lose more hair in the winter than we do in the summer, that's actually a myth. In fact, a 2009 study from the University Hospital of Zurich shows that people actually lose the least amount of hair in the winter. This makes sense from an evolutionary standpoint: We need more hair in the winter to help keep our heads warm, so we lose less of it.

Winter means shorter days and less time spent in the sunlight. During these months, we may find ourselves craving foods with vitamins and minerals that can help with Seasonal Affective Disorder—specifically, those full of B12 and zinc, says Lisa Richards, a nutritionist and author of The Candida Diet. Find yourself reaching for more beef, poultry, eggs, or fish? Your body might need some B12. If you're opting for red meat, nuts, and beans, you may need the zinc found in those foods.

When we get cold, our body tends to speed up our metabolism to help deal with the stress of extreme temperatures. In a 2014 study from the National Institutes of Health (NIH), researchers had five healthy young men live in a clinical research unit at the NIH Clinical Center in Bethesda, Maryland, for four months. They adjusted the temperatures in their private rooms every night, from 75 degrees Fahrenheit during the first month, to 66 in the second and third, and then up to 81 for the final month. After the second month, when the temperature first dropped, the participants had a 10 percent increase in fat metabolic activity.

"These alterations returned to near baseline during the following month of neutral temperature, and then were completely reversed during the final month of warm exposure," writes Carol Torgan, PhD, of the NIH—meaning the cold was affecting the study subjects' metabolic rates, specifically due to changes in hormones like leptin and adiponectin.

Brown fat, which you've probably heard referred to as "baby fat," is a type of fat that uses energy to generate heat, explains James Wantuck, MD, chief medical officer at PlushCare. Brown fat "was long thought to no longer be present in significant quantities in adults, but recent studies have shown that this wasn't correct," he notes. "It is now known that adults do indeed have brown adipose (fat) tissue and that it does respond to cold temperatures."

According to the same 2014 NIH study, after a month of exposure to the 66 degree room at night, the participants had a 42 percent increase in brown fat volume. "The findings suggest that humans may acclimate to cool temperature by increasing brown fat," Torgan notes. "These changes can be dampened or reversed following exposure to warmer temperatures."

When your body is cold, your thyroid gland gears up and sends signals to your organs to increase work, Topgi says. According to the National Institutes of Health, in situations when your body needs more energy—like when it's freezing outside—the thyroid gland produces additional hormones.

Have you noticed more neck pain and stiffness in the winter? Believe it or not, there's actually a correlation between those aches and the cold, as the team at Physiotherapy for Women in Lockleys, South Australia explains. Being cold actually causes your body to tighten up—it's an attempt to conserve warmth, but after a while, you start to feel the negative effects of bad posture. Oh, and remember those tightening blood vessels? In order to do that, muscles constrict, which can also cause discomfort over time. Your body is doing its best, but winter is a real pain in the neck.