On my way to the dry cleaners, I passed a gaggle of highschoolers on their way home from class. The high was 16 degrees yesterday, and the wind made it feel like single digits. But most of these students were dressed for a crisp fall day. One kid, some Justin Bieberesque boy on a bike, sported a sweatshirt instead of a jacket. The sleeves were pushed up to his elbows, leaving his forearms exposed. On his hands he wore lime green fingerless gloves. The girl next to him had a light coat that she had failed to button. Gusts of polar wind whipped it to and fro.
“Hell no!” I thought. “Go home and put on some proper winter clothes you dumbasses.” If it hadn’t been so cold I might have rolled down my window and yelled it.
I was stupid once too. In North Dakota, where I grew up, winters were brutal. Yet, as a teen I used to drive half an hour to school in a Dodge with a broken heater. And because it was the era of what my father calls “mall bangs,” I never wore a hat, even on those -20 days when the wind would freeze your nose hairs and steal the air from your lungs. On the coldest days, I might put my lightly gloved hands over my naked ears. Teenagers are idiots. But they also seem to be immune to the cold.
Now that I’m in my 30s, I rarely leave the house without a hat and gloves and scarf. I wear long underwear when I walk the dog. Outside, I shiver and swear. Inside, I drink mug after mug of steaming tea. I have made the space heater my constant companion. I have grown old and soft. I’ve lost both my youth and my cold tolerance.
Science has at least one explanation for this. The key is a substance called brown fat, which is nothing like the white fat that comes from excess cookie consumption. Brown fat is brown because it is chock full of mitochondria that work furiously to produce body heat. Scientists used to think that only babies, who are terrible at shivering to stay warm, had brown fat . But in 2009, three research groups simultaneously reported that some adults have it too. Researchers found these stores using PET scans, which highlight areas of metabolic activity. Because brown fat cells are like little furnaces, they light up. But our brown fat stores tend to shrink as we age, and what little remains becomes less active. Incidentally, brown fat seems to spike during late puberty. So maybe teens really are immune to the cold.
Here’s the good news: We may lose brown fat as we age, but there are ways to get it back. A couple of years ago, a team of researchers recruited 17 healthy men and women and asked them sit in a 60-degree room for six hours a day for 10 days. The volunteers, dressed in t-shirts and shorts, passed the time watching TV or studying. On day three, the volunteers were shivering and feeling uncomfortably cool. But by day 10, they were accustomed to the cold. They shivered less, and their discomfort had eased. And PET scans showed that their deposits of brown fat had increased by 37%.
Another study, called Impact of Chronic Cold Exposure in Humans or ICEMAN, looked at the impact of cold on five healthy young men. The volunteers could do whatever they wanted during the day, but each night they had to spend at least 10 hours in a room at a research facility. The first month, the room was 75 degrees, the second month 66 degrees. Then, for the third month, the team boosted the temperature back up to 75 degrees. The fourth month the room was even hotter, a steamy 81 degrees. No matter what the temperature, the men had to wear scrubs, though they also had sheets on the bed to use for warmth. After the second month, the volunteers had 42% more brown fat and a 10% increase in metabolic activity. But during month four their stores of brown fat shrunk, and they ended the study with less brown fat than they started with.
But here’s the catch-22. These studies suggest that to become more tolerant of the cold, I have to do the one thing I don’t want to do: expose myself to it. No thank you. I’m quite comfy under this blanket.
Here’s what I really want to know: How much of my midlife cold aversion is physiological and how much is mental? We already keep our thermostat at 68 degrees. That’s not much warmer than the rooms where the men in the second study slept. Maybe my problem isn’t a lack of brown fat but rather a bad attitude. Perhaps I just need to decide to enjoy winter. Just don’t make me give up my space heater.
Image credit: Glen Euloth on Flickr