This thread is just for fun while waiting to go winter camping...

I keep seeing some version of the following argument in winter camping/backpacking articles, blogs, videos, etc:

...if you hold your pee in at night, your body has to keep the urine warm and this will require energy expenditure and make you colder...

I disagree, things get warmer or colder by gaining or losing heat, and it's temperature differences that drive heat transfer. The fluid inside your bladder got there from elsewhere in your body, so it was already at body temperature. And it's completely surrounded by heat-producing tissue, so there's no avenue for heat loss from the urine that would tend to make it colder. So it shouldn't require any heat input to stay at body temperature. Technically there's a steady exchange of heat with the surroundings as part of being in equilibrium, but it doesn't draw any more heat from your body than it gives back. So you're not expending any energy keeping your urine warm.

There may be some physiological details that I'm not considering, but I'm skeptical that they would change anything.

Maybe it's easy to confuse the "I have to go!" feeling with the "I'm cold!" feeling, they are similarly uncomfortable sensations.

The whole thing is moot anyway, since I do agree it's better not to hold it in - for comfort reasons, and because it forces you to get up and go out and look at the stars! And the feeling of crawling back into your warm bag after relieving yourself is heavenly.

Any other thoughts or opinions? Anything I'm missing?

I don't think it makes you colder. If I can mentally block it out and sleep longer I at least feel warmer and more comfortable. A pee bottle is great for winter camping, I wouldn't want to get out of my tent at -15F!
On a side note I've been experimenting with finishing my showers with cold water for 2 minutes. Real game changer for temp fluctuation comfort. I used to freeze when we had a 40 degree day and then 20 the next, now it doesn't phase me. Seems to really help your body regulate temps.

I would think that it's such a negligable difference in heat retention that nobody would notice, and those that do only notice something similar to being colder but I'm not a urine retention-somnolent-heat retention academic.

I'm in the "get up and go camp". I personally I have a hard time falling asleep if I've clearly got to go. The bottle approach is a great option, just remember to empty them before they freeze! You don't want to be the guy warming up bottles of urine around camp. Or maybe you do! To each their own.

I tried a pee bottle once and didn't like it. I made the mistake of putting it outside of my sleeping bag when I was done, but then I had to pack it out frozen. I don't want to leave it in my sleeping bag either, I'll just get up, regardless of the temperature (it's very easy to sound tough about that from behind a computer).

I would be interested to hear the opinion of someone with more physiological knowledge than me (which wouldn't take much). Is there a "urine retention-somnolent-heat retention academic" in the crowd?

Failing to hold it in makes you warmer. Then colder again.

The conventional wisdom is that it makes you colder because your body has to heat more mass (think of keeping a bottle of water warm, you'll need a larger heater and more energy to keep a larger bottle warm than a smaller one all other things equal), but if you get up and out of your sleeping bag to go that will cool you down as well so I've always considered it a wash.

I have a bit of a mountaineering background and there are times where you just really don't want to leave the tent at night because of horrible weather. Learned to use a bottle without leaving the sleeping bag (there's a learning curve there, but once you figure it out it's a non-issue). Once you figure it out then you don't have to choose. Use a good bottle that won't leak and keep it in the bag with you (just shove it down by your feet).

This is a classic question. Think about the extreme condition. What if your body was small and your bladder was very big. Say your body was 10 pounds and your bladder was able to hold 100 pounds. Of course, your body would expend a lot of energy to keep your bladder warm.

Learn to use a pee bottle at night if you are a winter camper. Don't get out of the tent. Don't get out of the sleeping bag.

bobbernumber3: "What if your body was small and your bladder was very big"

That would be great, you'd probably only have to go about once a month! ;)

Considering hypothetical extremes is a good way to think, I think ;) But in that case the bladder would by necessity be greatly exposed to heat loss to your exterior (you'd be all bladder). And the ratio of metabolizing tissue to non-metabolizing mass would be tiny. And the actual situation is really the opposite extreme - a 200 lb body and a 10 lb full bladder mostly buried inside the core of the body.

keth0601: "you'll need a larger heater and more energy to keep a larger bottle warm than a smaller one"

It only takes more heat to keep a larger bottle warm than a smaller bottle if the larger bottle is losing more heat than the smaller bottle. If neither of them is losing any heat then it takes zero heat to keep either of them warm.

There probably is a temperature gradient across (and therefore some heat loss through) the bladder (as-in, one side of the bladder is closer to your warm core, and the other side is closer to your skin). But that same temperature gradient exists from your core to your exterior in any part of your torso, is the rate of heat loss significantly greater through a full bladder than elsewhere? Enough to justify so many youtubers listing "don't hold in your pee" as a tip for staying warm while winter camping? Why don't they stress the importance of not holding in your #2?

It's all good, I'm arguing this (and making a mountain out of a molehill) just for the fun of it. :)

keth0601: "Learned to use a bottle without leaving the sleeping bag...
...Once you figure it out then you don't have to choose."

and

bobbernumber3: "Learn to use a pee bottle at night if you are a winter camper. Don't get out of the tent. Don't get out of the sleeping bag"

I might reconsider for more extreme mountain or arctic conditions, but for winter camping in the bwca I think a pee bottle is a personal preference thing. I'm not saying it doesn't work great for some people, but I tried it and didn't like it.

Maybe I'm lucky that I sleep warm, but In my experience all I need is some fuel to burn (i.e. food and adequate hydration for metabolism) plus an adequate sleep system (good sleeping pads and a good sleeping bag and/or quilt). I don't use any extra techniques to sleep warm, like a hot water bottle in my sleeping bag or doing jumping jacks before bed, and I'm not concerned with the small amount of heat I lose by getting up at night to pee.

And the stars might be out. That's one of the things I go winter camping for...

schweady: "Failing to hold it in makes you warmer. Then colder again.
"

I had a friend who did exactly this on a night around 0 degrees. He spent most of the night drying his sleeping bag out over his stove. I suspect he had been drinking. I also suspect his winter camping buddy did not appreciate the smell.

I think holding it in just makes for a more restless sleep, whether or not your body is running at the highest efficiency. I haven't had the chance to utilize a pee bottle but I am not inclined to bring one as it is another piece of equipment to keep track of, add (minimal) weight, and complicate matters. Plus, if I didn't get up out of my cozy sleeping bag (which feels like once an hour) I would have missed this:

When you have to pee go pee. I don't get cold while sleeping, but it will keep me awake if I try to wait it out.

Get up, look at the sky, pee and go back to sleep.