Advice - Fasting hypothermia

How are you measuring and are you sure your thermometer is accurate? I understand that the medical profession have recently realised that is some variability amongst people's normal body temperature (some people are colder, some are hotter, there are variations based on time of day, activity level, etc.)

This is quite interesting (I read a similar story in New Scientist sometime back which I remembered and prompted me to respond): https://www.scientificamerican.com/article/are-human-body-temperatures-cooling-down/

There are also some links to journal papers which may be of interest from the Wikipedia page: https://en.wikipedia.org/wiki/Human_body_temperature#Variations

I suppose the question is then is this lower apparent temperature causing you problems? You mention catching colds, could that be more down to lower energy levels producing depressed immune system response rather than cooler bodily temperatures suiting the cold virus better? I don't know.

So you're seeing a swing of to 2C on armpit temperature between normal days and fasting (first thing in the morning)?

From my very quick glance at the literature, a swing of 2C doesn't seem all that terrible, and armpit temperatures can be both higher and lower than core temperatures anyway from a quick look of the data (and which makes sense depending upon your core heat generation and ambient temps).

So I think I'd go back to my earlier question re is it causing you problems, and if so, is it actually the core temperature which is the issue or the lack of energy availability? Other than that, sorry, I don't have anything to suggest.

@IamResistance - not sure if you have read the thread that @lovinglife pointed at, but it does sound quite similar to what I was describing on the second night of a 36 hour fast.

I cannot know for sure that this is correct, it just seemed to make sense - I was watching a lecture that was breaking down why a recent study claims that Keto can damage the thyroid, and the conclusion was that while thyroid hormone does seem to reduce with lowering blood glucose, thyroid hormone signalling does not - in other words the thyroid itself is fine, you just need less - much the same as you would expect insulin levels to go down, but do not suspect that the reason for this with lowering blood glucose is that your pancreas is being damaged by diet.

- to be clear - this lecture was explaining why the study was wrong to suggest damage to the thyroid.

That was just ...interesting... but it was when it went on to explain that the job of the thyroid hormone is to both escort glucose into the cells (ie, that's why you need less if you are using less glucose for energy, and more fat) - but also that it helps activate the process that makes certain fat cells generate heat energy - it's kind of our inbuilt central heating. And that gave me a bit of a lightbulb moment.

In other words, could this be an unexpected consequence of longer fasts - that acutely, because your blood glucose goes right down (which it definitely does for me after about 24 hours), you will also acutely have less thyroid hormone than normal, and thus feel abnormally cold..

.. even if you are generally feeling toasty when not fasting, under the same conditions.

IamResistance said:

Might I ask you if you are also experiencing body temperature lowering?

Click to expand...

Might I ask you in return whether you did read the other thread? - it's literally titled "Feeling cold at night at the end of a 36 hour fast"

Unless I'm misunderstanding your question, which is perfectly possible...

Understood - thanks for the clarification.

Ok - so, no, and I suppose I should have checked myself, given that I wear a watch that can monitor exactly that - **DUH moment**

So - here is a normal graph:


This was the day of the start of the fast,
This was the second day

So - I went paddleboarding around 8am when the sun came up, no excercise during the day, which maps to very stable temp... and then;


this is the troublesome night, where I was struggling to either sleep (though handily the graph shows when I managed to)
or keep warm..

So - I think there is some evidence here that my actual temperature changed for no good reason during the night..
I'll keep more of an eye on this graph from now.. (too much data as it is, really..)


As a total baseline - I think I had a really restful day yesterday - no stress, no exercise - this is the plot:

<takes a second to remember which thread this is>

OK - so, to be clear - this thread is about fasting Hypothermia and getting a cold infection as a result (or coincident with) long fasting.

Any form of eating regularly means that you will be primarily fuelling from food that you have recently eaten. That's fine (and I'm not intending to make a judgement of what is "best" - but I think the point of longer fasting (or any form of not-eating) is about driving a process of becoming fat adapted; or the opposite of your body expecting to fuel itself primarily from food recently eaten.

So - we would expect some differences in experience, especially in the transition.

as @IamResistance pointed out, there is a huge difference between core body temperature measurement and what you "feel" - which is mainly down to the hypothalamus (I think...)

There is clearly a connection between "feeling cold" and being infected with rhinovirus - otherwise we would not be calling it "catching cold" -

The main thing I was reflecting on in my other thread, is that I felt unusually cold - (and in a massive leap to my NAFLD last post, there may be a connection to feeing cold under the short term hypothyroidism - if that's what it is, and the hot flashes that come with menopause for some women - that being an overstimulation of the same system from lack of the hormone that would normally keep it under control... but I digress).

I was, and still, struggle to describe exactly how it felt unusual, but against a general background of feeling warmer, that night as soon as l lay down, my legs just would not warm up. I could get up, walk about a bit - fine, then lay down again, and they got cold, but no cramping, which is what usually happens for me if my feet are cold.

I personally do not feel any more likely to catch a cold - but I haven't had a cold now for over two years (actually, not true; I had one about a month ago - it lasted an hour and a half) - I have reliably had colds all my life, about once every couple of months, with about one a year that floors me - so this is extremely unusual. (for me).

I think the traces I shared above are only kind of interesting - I'm not aware of any of these fluctuations, the only thing that is interesting to me is when I'm struggling to sleep, there is a sudden dip in temperature, that resolves, suddenly - when I get to sleep.

Most nights, I'm -0.3 degrees - which is normal - one of the big circadian triggers (one of the ways you can train your circadian rhythm) is that your body likes to see a ~1°C drop in core temp as a sign you are ready to sleep. Ie, "being" a little colder is fine - "feeling" oddly cold is not.

Reading that article (again?) -

I'm kind of so immersed in this at the moment, that every piece of information is now building on others - like that part of doing a jigsaw puzzle were it seems to start getting easy, because you can see the general picture - before it gets harder again...

So - one of the reasons I tend to go paddleboarding at daybreak in Yorkshire in December, is precisely because you can be just the right amount of cold - cold but not shivery.. which stimulates brown fat to produce heat (in a process that I now understand - mitochondrial uncoupling - but I'm not going to explain that).

Also walking at night with a thin fleece - if you walk fast, you are not shivering cold, but you are definitely cold - all of this burns body fat - IF - your metabolic state allows you to burn any body fat - insulin rules if it's around.

The gist of the article is - yes, cold works (if not so cold that you shiver - basically this means your hypothalamus has decided you are too cold, and needs to call in the cavalry). Exercise - that's a bit more nuanced.

[hysterically well timed - I just got a message from my GP surgery - "our health & wellbeing coach can help support you to take a more active role in your own health through diet, exercise or other lifestyle changes". I'm going to book an appointment to see what they make of me...]

interestingly - the whole article is written from the perspective of "what does cold and exercise do in brown fat cells in the presence of abundant glucose" - so it's clear that this is beneficial (both exercise and cold) for glucose clearing and insulin sensitivity by different mechanisms, and while it does mention that while mitochondria can produce both heat and energy from other fuel sources - that condition is not tested - so it doesn't actually answer the question we started with - what is happening at the end of a long fast - where you are expecting the cells - all of them and particularly fat storage cells - to be more reliant on fatty acids and ketones for fuel than glucose.

for what it's worth (and this may be a couple of steps too far, but bear with me) - the goal I'm aiming at is not clearing blood glucose per se... I think that can be done without the effort of fasting (for me, now) - but to re-constitute my cell linings and fat stores with better quality fatty acids than the seed oil derived unstable (and oxidisation prone) fatty acids that must be there (and I think is probably at the heart of my question too, because they will not be capable of providing the energy - thus feeling cold) from my use of seed and vegetable oils for years - and this will be a ~2 year project minimum...