My Partner Hates the Cold. I Love It. We Can't Stop Fighting. Whose Fault Is It?

We've been improving our understanding of human comfort for decades. But the mechanisms that actually keep the body warm are still mysterious—and wonderful.

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Several years ago, I took a woman from Long Island out on a first date. French restaurant in Brooklyn. This was in mid-February, a week or so after we’d met at a party thrown by a mutual friend. I arrived early at the subway stop nearest the restaurant—I was nervous. When she showed up, bundled in a peacoat and a gigantic scarf and earmuffs, we slipped easily into conversation and started walking to dinner. We’d gone maybe two blocks when she started asking how far we had to go. I guessed; I’d never been before. It’s just really cold, she said. We kept walking, and the blocks got longer, and her questions about the restaurant grew more frequent. I was enjoying the walk, but she was acting like the guy in that Jack London story who gets so numb his hands won’t work to build a fire. I was fairly certain I’d squandered my chance with this woman, whom I really liked. (Spoiler alert: The guy in the Jack London story dies.) Luckily, we got to the restaurant, and it had not only French wine, which makes you feel warm (though—caution!—doesn’t actually warm you up)—it also had a giant fireplace and a roaring fire. We got a table practically inside the hearth, and everything was great.

Until it was time to leave.

We’ve been on the walk home pretty much ever since. Because while we made it to a second date, and a third, and many, many, more, every year when it gets to about this time, I look out the window and cheer the end of summer, and she looks out the window and frets about the winter, and we kick off a season of fighting about how she can stay warm if we’ve got to go outside in the cold. I say to put on more layers and she says that never works and I say the walking will keep you warm and she says cutting through the wind gives her brain freeze and we ultimately reach a stalemate and flip a coin and half the time we just stay in and order pizza and binge Veronica Mars. (Which isn’t so bad, really.)

But a few years ago, the fights tipped in her favor, as a story made the rounds about the fact that offices are objectively too cold for women, because comfort standards are based on an old formula that factors in how much body heat people generate at rest—using as its prototypical human a 40-year-old, 154-pound dude. Women, whose metabolic rates are generally lower, generate less heat. But we weren’t fighting about the office, we were fighting about the outside. So this year, I decided to find out exactly how this works: Are men and women truly different when it comes to handling the winter? Do some people just run cold, and others just run hot? And is there anything to do about it?


Technically speaking, of course, we all run hot. We’re endotherms, meaning we generate heat ourselves. We’re also homeotherms, meaning that we keep our body temperature stable, at roughly 98.6°F. In a comfortable environment, our basic metabolic functions generate heat to maintain this temperature. If it’s too hot or too cold, our body takes measures to counteract the environment. In the cold the body tightens up blood vessels—this is called vascoconstriction—keeping blood out of the extremities, where it’s liable to cool very quickly. If things still aren’t warm enough, we shiver, which generates more heat but uses more energy.

It’s one thing to understand how the body makes heat, and another to understand what mix of body heat and environmental factors make someone feel comfortable. Scientists have been building ever more sophisticated models of this for more than a century now, and in fact, this kind of model is what received scrutiny in the article that exposed sexist office thermostats. That was written by two researchers at Maastricht University Medical Center in the Netherlands. As I was trying to make sense of temperature models, hoping one would provide some kind of winter-date life hack, one of those researchers’ names kept popping up: Wouter van Marken Lichtenbelt, a biologist who leads the Thermophysiology & Metabolism research group in Maastricht. I decided to give him a call.

Wouter spoke to me over Skype, sitting in front of a wall of books and apologizing for the fact that he was fighting off a minor cold. I explained my basic query, and he immediately pointed out that there are key thermal differences between men and women. Women are smaller, on average, which means they cool faster, thanks to a higher surface area-to-volume ratio. And more important, women have relatively less fat-free tissue than men—and fat-free tissue is where most of our heat generation takes place. “If you put men and women in the same environment, on average the woman feels cooler,” he said. “She also loses heat to the environment, and her heat production is less.”

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So, There's a Thing Called Brown Fat

Wouter also talked about something I’d never heard of before: brown fat. Unlike your garden-variety white fat, which is really only good as insulation, brown fat generates heat when the body activates it. It takes more energy than vascoconstriction but less than shivering. It’s common in small animals, like mice, and animals that hibernate. But until Wouter and a team of colleagues made the discovery about a decade ago, no one realized humans hadn’t evolved away the ability to use it to keep warm.

The key thing to know about brown fat, as Wouter tells it, is not so much that it generates heat as that it indicates the body’s ability to adapt to cold. In the summer we don’t have much of it, but when we’re exposed to the cold as temperatures drop in the fall and winter, our bodies add more of it. So early in the cold season, at least, I probably have real advantages over my partner Laura: Men have some basic physiological reasons they're able to keep more comfortable when the mercury drops, and sure enough, when we enter December and January, I still walk a few extra blocks to the more convenient subway stop, I run just as many errands on foot, and I always, always eschew the treadmill in favor of the park. I'm sure I acclimatize faster than she does.

Wouter confirmed that acclimatization is important, but reminded me not to overlook body composition. “I must stress, it’s often misunderstood,” he said. “I don’t think brown fat is the only thing. I also think, even without shivering, that muscles also may play a role. It’s not only brown fat. It’s the interaction of brown fat and other issues that is important.”

Laura, by the way, has her own theory about why she’s so prone to feeling cold to her marrow. Her mom tells her she was heavily swaddled as a baby—over-swaddled, she thinks. What if that formative experience prevented her body from learning to acclimatize?

I ran this by Wouter, who regarded it with real interest, but said there wasn’t much science to indicate its viability one way or the other. It turns out that longer-term temperature adaptability, things like youthful experiences and genetics, are generally understudied. “I don’t know if your youth really influences it…I would expect it. It’s very well possible,” he said. “That’s my careful answer.”

“What could also help with your partner,” Wouter told me, “is to have her exposed regularly to the cold.” In other words: If you really want to go on more dates this February, just lock your girlfriend out in the cold every now and then! (“Though I don’t think she’s going to like it,” he admitted, laughing.) Working from a body of knowledge that had emerged from painstaking hours of research, Wouter had many notes that would collapse in one poorly-worded moment in a relationship. Women have a higher body-fat percentage, and all that body fat doesn’t help you make heat. But: “If you have a lot of fat, then it is an advantage again,” he said. If you really want to go on more dates this February, just get your girlfriend fat first! (French food?)

Assuming you’re trying to stay within the bounds of maintaining a healthy relationship, most of what I learned from Wouter mainly confirmed that women are at a disadvantage on a winter’s night—they’re smaller on average, so they lose heat faster, and their physiology makes it harder for them to generate more of it. But he also suggested that there is a fair amount of mystery still remaining about thermoregulation in humans—about avenues, like genetics, as yet not fully explored. And it struck me that while everything Wouter covered was about individual physiology, my experiences every winter had a particular social dynamic to them. This seems to be an extremely vexing issue for couples. Does that matter at all?

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The Human Penguin Project

With these ideas clanging around in my head, I came across a research paper called The Human Penguin Project. It was a study of what’s called “social thermoregulation”—the extent to which social interaction is a part of how we regulate our body temperatures. I got in touch with the lead researcher, Hans IJzerman, a social psychologist at the Universite Grenoble Alpes in France. “Throughout the animal kingdom, decreases in temperature are often dealt with by outsourcing to other animals,” he told me. “The famous animal that does this is penguins: When penguins get cold, they all huddle up. And really, basically every homeothermic endotherm does this. Even non-social endotherms still huddle with one another if the temperature drops.”

But the point of the project wasn’t to find out if humans ever huddle for warmth but to explore whether other social behaviors could have any bearing on our core body temperature. “We may not need to rely on others as much anymore to regulate temperature, as we have invented clothes and central heaters,” IJzerman said. We’ve had heaters for a lot less time, evolutionarily speaking, than we’ve needed shelter from the cold, though. “We still kind of associate being with others with temperature regulation.”

What the Human Penguin Project found is that there is actually a positive correlation between more diverse social networks and higher core body temperature. Furthermore, the farther people live from the equator, the more diverse their social networks tend to be—perhaps as a way of keeping their core temperature high in the face of a colder environment.

IJzerman told me about many interesting aspects of social thermoregulation. There are older findings that have shown that our skin actually gets hotter when we’re angry and cooler when we’re sad (another way to “run hot” and “run cold”). IJzerman’s lab did a study where they found that in romantic partnerships, if one member looked sad, the other’s peripheral temperature would increase, to compensate. Though he’s quick to point out that these findings still require further study. He theorizes that this phenomenon could present a way to use temperature differences to predict the strength of a relationship. He also wants to use a new “personal thermostat” device, the Embr Wave, to manipulate body temperature and study its effect on interpersonal relationships.

That introduced a whole new line of questioning for me. I love being outdoors in the winter, but indoors, I often find myself stomping around, irascible, hotter than I can stand. Meanwhile, Laura is pleading with the radiator to turn back on. Could it be that I run hot in part to compensate for her eternal winter sadness? Could it be that I get warmer when we’re out on a date because my body is trying to compensate for her deep freeze? I think it’s unlikely the affect would be that big—IJzerman’s research on this point is not yet conclusive—but somehow it made me feel better to know that our fates could be intertwined.

Indeed, the line of research IJzerman was traversing was more encouraging than what I learned from Wouter, not so much because its effects were stronger but because it felt like something you could change, in ways other than standing out in the cold to get your body to pump out brown fat, or pumping iron for months to build up muscle. And isn’t this what we need to hear most winters: Diversify your social network! Huddle for warmth! If you want to make it through winter, connect with people, for godsakes! Plus, anecdotally, I must say that it stands up. A couple years ago, Laura and I moved in together, and the place we found just so happened to be around the corner from the subway stop from our first date. Just this year—in February, in fact—February again!—I decided it was time to return to the French restaurant for the first time. On the way home, I steered us into a park, knelt down under a big tree, in the dim light of a winter evening, and proposed. We walked out of the park arm and arm, and she didn’t seem so cold.

The Thermophsyiologist's Guide to Winter

Once you understand how the body manages its temperature, you can make some critical adjustments to stay a little bit warmer. But first: Wear a few more layers. It really works.

  • Mind your extremities: Just as women cool faster because they’re smaller, and thus have a higher surface-area-to-volume ratio, body parts like fingers and toes suffer from the same problem. And research has shown both that temperature at the fingertips has a large bearing on how cold people feel, and that, for women in particular, cold extremities tend to decrease overall comfort. So bring a hat, mittens, balaclava—whatever it takes.
  • Keep exercising like you did in summer: Heat generation comes from non-fatty tissues. Muscle, in particular, is helpful (even when you’re not shivering). So since unhealthy holiday meals are probably unavoidable, try to find ways to at least not skimp on exercise.
  • Don’t shrink from brisk fall days: Acclimation is a real thing. Your body physically adapts as it starts to experience dropping temperatures. When it starts getting cold, find reasons—within reason—to get outside and enjoy it. In February, your body will thank you.
  • Check out the Embr Wave: The “personal thermostat” isn’t going to keep you warm when it’s freezing out, but for minor adjustments when office thermostat isn’t accounting for the cold outside, or the radiator is overdoing it at home, it can make enough of an adjustment to get you comfortable.


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