Why am I so hot?

July 30, 2012 1:54 PM

Why is there such an extreme variation in the way humans perceive and react to the same ambient temperature? Especially in the way I perceive it relative to everyone else around me?

I tend to be significantly warmer that most people around me in most situations--that is, I feel like I am warm (as opposed to my internal temperature being higher or my skin feeling warm to the touch) while everyone else around me feels cold. I know everyone's different and there are tons of little not-well-understood variations between human bodies that account for people not perceiving sensations the same way, but this seems to be an extreme variation. I show up for morning bike rides and I'm already starting to feel pleasantly-to-uncomfortably warm while everyone else is shivering in their arm warmers and tights and kindly offering me their jackets. I walk through San Francisco on foggy evenings perfectly comfortable in my short sleeves and strangers cannot resist commenting on how cold I must be. It's not just that I'm warm when others are cold; I can't handle the heat, either. During a recent outing in 95degF weather everyone else was sweating and a little uncomfortable but I was absolutely miserable and could barely handle it, despite being vigilant about staying hydrated and wearing cool, breathable clothes.

Relevant info: I'm a plus-sized woman in my early 30s. I have high blood pressure that's under control with medication but am otherwise in reasonably good health. This has been the case for as long as I can remember, and has remained constant through weight fluctuations, changes in lifestyle and activity level, and moves back and forth across the country. I am equally miserable in dry heat or humidity. I do get cold, too--other weather conditions notwithstanding, 40degF is about when I start feeling cold enough to be uncomfortable and want to do something about it.

So what gives? I sometimes joke with people that "it's all the extra insulation I have!" but I know other people my size who don't overheat like I do. I have a few friends who experience the opposite--they are always freezing--and they attribute it to poor circulation. Is there a similar physiological explanation for why I'm almost always so hot?

posted by rhiannonstone to health & fitness (20 answers total)

Me too. I have a theory that it's just to do with what you grow up with, but no evidence for it.
posted by katrielalex at 2:03 PM on July 30, 2012

Wikipedia has some good information on variance in thermoregulation.
posted by desjardins at 2:16 PM on July 30, 2012

To some extent, your plus-size is a factor because it gives you a lower surface to mass ratio, which causes you to retain more heat. You may wish to compare the body types of Inuit (shirt and stocky) with those of Zulu (tall and lanky).

This will not account for 100% of the variance, but it is certainly a factor.
posted by Tanizaki at 2:17 PM on July 30, 2012

katrielalex, I don't think that's the case for me. I grew up in eastern North Carolina, and the hot, humid summers were miserable for me there, too. I was an indoor kid in the summer and had to be forced to go outside. Which seems to mystify the people who see me suffering in the heat and say, "But you grew up in the south! Aren't you used to it?"
posted by rhiannonstone at 2:18 PM on July 30, 2012

I have a few friends who experience the opposite--they are always freezing--and they attribute it to poor circulation.

I am cold all the time and my doctor said it was probably a combination about this and the fact that I have extremely low blood pressure.
posted by cairdeas at 2:27 PM on July 30, 2012

(Just noticed that you actually said in your post that you high blood pressure!)
posted by cairdeas at 2:28 PM on July 30, 2012

Everybody's natural thermostats are set differently, and how they differ is complicated. Your sensation of temperature is affected by:
1. Metabolism. A higher metabolism means your body produces more heat than normal, a lower metabolism means you produce less. This is mainly affected by your thyroid gland, which you can get easily tested.
2. Sweat glands. Some people just have more sweat glands than others and sweat/cool more efficiently. Living in a hot climate forces your body to produce more sweat glands so you sweat more but feel cooler.
3. Body fat %. The higher body fat % you have, the better insulated you are and the warmer you feel.
4. Muscle %. A higher muscle % is complicated. You have a higher metabolism so you produce more heat, but you have more blood vessels so you feel more cool. Overall muscle tends to make you feel cooler.
5. Blood pressure. High blood pressure generally means you feel warmer because your blood is being pumped to your organs. Low blood pressure means you feel cooler because your blood stays in your core.
posted by TungstenChef at 2:49 PM on July 30, 2012 [1 favorite]

I am a person who is always cold. I was playing with an infrared camera along with a bunch of other people, and noticed that I had a lot less emission from my extremities than most of the people there. My hands and feet and nose actually *are* colder. I'm not sure what the reason for that is. I do have low blood pressure.
posted by pizzazz at 3:09 PM on July 30, 2012 [1 favorite]

I think this is attributable to a lot of different things.

For one thing, I'm pretty sure that physical size has something to do with it. I was a skinny child and as an adult am short with an average build. I've always been "cold natured". I don't think I've ever met a warm natured slim/petite person or cold natured large/bulky person (for either height or build). I don't know that "fat" necessarily makes you warm natured, but I'd guess that physical bulk does.

Also, I think it has to do with things that vary highly from person to person, like hormones, blood pressure, metabolism, circulation, etc.

Thirdly, I think there are a lot of regional variations, especially if we're talking about environmental temperature and not just whether a room is stuffy or whether the AC is on too high. I grew up in a hot, humid part of the US and deal with heat and humidity pretty well. I feel hot, but it just doesn't bother me that much. Meanwhile, I know a lot of people here in the north who go apoplectic at the idea of a 90 degree day, but do just fine in frigid weather. Meanwhile the prospect of anything below 0 Fahrenheit makes me want to die. In almost 15 years living up north, I haven't adjusted to the winter very much at all. I'm better about choosing a pair of boots or wrapping a scarf efficiently, but I still fucking HATE THE COLD.
posted by Sara C. at 3:23 PM on July 30, 2012

My brother and I are total opposites re: thermoregulation. I am always cold, and he is always hot. We grew up in the same house (mostly cold) and have similar body types (tall and burly).
posted by Sidhedevil at 3:29 PM on July 30, 2012

Total theory here, but a symptom of hypothyroid is not being able to stand the cold, while a symptom of hyperthyroid is feeling hot/sweaty. This is not to say that you would necessarily have one or the other, but perhaps natural differences in thyroid hormone affect whether or not you run hot or cold?

Also, random data point: I tend to feel extra cold in most circumstances and I have silly low blood pressure. However, I cannot bear much heat at all while exercising. The reason for that (I think) is because I am a very inefficient sweat-er.
posted by smalls at 4:11 PM on July 30, 2012

Heat Acclimatization:

What is heat acclimatization?
a. Heat acclimatization refers to biological adaptations that reduce physiologic strain (e.g., heart rate and body temperature), improve physical work capabilities, improve comfort and protects vital organs (brain, liver, kidneys, muscles) from heat injury. The most important biological adaptation from heat acclimatization is an earlier and greater sweating response, and for this response to improve it needs to be invoked.

How do you become heat acclimatized?
Generally, about two weeks of daily heat exposure is needed to induce heat acclimatization. Heat acclimatization requires a minimum daily heat exposure of about two hours (can be broken into two 1-hour exposures) combined with physical exercise that requires cardiovascular endurance, (for example, marching or jogging) rather than strength training (pushups and resistance training). Gradually increase the exercise intensity or duration each day. Work up to an appropriate physical training schedule adapted to the required physical activity level for the advanced military training and environment.
c. The benefits of heat acclimatization will be retained for ~1 week and then decay with about 75 percent lost by ~3 weeks, once heat exposure ends.
- Heat acclimatization guide. US Army (PDF).
posted by Lanark at 4:24 PM on July 30, 2012 [2 favorites]

When I was on Prozac, I was always hot. Always always always. I was even hot in my underwear sitting in front of a fan in the winter.

So if you're on meds, it could be related.
posted by tacodave at 4:47 PM on July 30, 2012

There are subjective factors and variations in how different bodies manage heat, but it also has to do with the surface area to volume ratio of your body. This ratio changes with shape and decreases as your size increases, so an elephant must have huge ears to increase his surface area and radiate heat, whereas a hummingbird must eat nectar all day to keep warm. To understand how this works, here's an example:

Take a sugar cube person. Lets say he is one square centimeter per side. He has six sides, so his surface area is six square centimeters. His volume is one cubic centimeter, so the surface to volume ratio is 6/1, or 6. Now take an eight sugar cube person, (stack them into a larger cube, with four on the bottom level and four on the top level). He has exactly the same shape (a cube), and let's assume he has the same internal temperature, but he is larger. His surface area is now 24 square centimeters, and his volume is eight cubic centimeters, so his surface to volume ratio is now 24/8 or 3, which is half the previous ratio. That makes it twice as hard for that eight cube guy to radiate heat, compared to the one cube guy. Now take those eight sugar cubes and line them up in a row, like a tall, skinny eight cube person. The area is now 34 square centimeters, so the ratio is 34/8 or 4.25, so it's way easier for him to radiate heat and stay cool, even though he weighs the same.
posted by weapons-grade pandemonium at 5:13 PM on July 30, 2012

I'm like this too, except my blood pressure is normal. There doesn't seem to be anything wrong with me -- thyroid seems fine, etc. -- I just tend to be a lot warmer than other people. It's irritating!
posted by sarcasticah at 5:45 PM on July 30, 2012

This is me also. I don't have high blood pressure, though. I am overweight, but never was growing up, and I have ALWAYS been extremely intolerant of heat.

My husband didn't believe me when we first started dating. Then we walked six blocks in downtown Chicago in August. He believed me after that. I had to go into a store to get in the A/C. My face was beet red and I felt like I was ready to pass out.

I hate it. This huge heat wave we've had this summer has me holing up in the house. Unfortunately, I have little kids who would LOVE to play outside, so I'm depriving them, too. Plus I get jealous when I see pics on facebook of everyone out and about, having fun despite the heat. I mean, running a 5k in this stuff? Are you nuts?!
posted by wwartorff at 7:44 PM on July 30, 2012

The way I learned it is this: when our body temperature drops below a certain point, our body does certain things to reduce heat loss, such as shiver. When our body temperature is above another point, our body does certain things to increase heat loss, such as sweat.

There are factors to consider which people have mentioned, such as weight/build, activity level, acclimation, blood pressure, medications, etc. These factors might make you especially prone to heat intolerance if the temperature at which your body's A/C kicks on is different than the average person.
posted by gumtree at 10:06 PM on July 30, 2012

Here's an interesting data point for you: my sister recently lost a significant amount of weight, going from close to 300 pounds to close to 200. One of the things she noticed that was different was that she feels a LOT less warm than she used to. She used to go out in short sleeves in the winter, was always complaining about how hot it was when everybody else was comfy, etc. Now she's wearing long underwear in the winter for the first time (she had to ask around where to get it, since she had no experience with it).

In my case, my weight's about what it's been my whole adult life, but I've noticed that I'm a lot less warm the last few years (I'm 47); this has been gradually changing since my early 40s. (And this has nothing to do with anything, but why does nobody tell you how much your body changes in your 40s? I've dealt with HUGE changes. Then again, maybe it's just me.)
posted by WorkingMyWayHome at 10:15 PM on July 30, 2012

When I used to do a lot of diving and surfing you really noticed the people who could deal with cold vs people who couldn't and it's pretty random imho. You'd have a person in an insulated drysuit freezing their ass off all day long, even in the boat, and then another person in a shortie wetsuit in the water for the same amount of time and they'd be perfectly comfortable. Age, sex and size seemed to have little to do with it, admittedly none of these folks were terribly overweight or out of shape but certainly plenty of variation.
posted by fshgrl at 11:35 PM on July 30, 2012

Another vote for thyroid it controlls the body's tempurature regulation.

Also you can get used to temperatures. My parents keep their house up in the 80's during the summer and it took a while to get used to, but once I got used to it it wasn't so bad.
posted by eq21 at 3:37 PM on December 6, 2012