The FastDay Forum

Some years ago, brown adipose tissue (BAT) was making a name for itself as being important in people who are naturally lean. It was thought that as infants we all have BAT, but that it disappears as we grow up apart from in some people who turn out to be naturally lean.

Since then researchers have found that actually BAT is present in everyone (link) and that the amount is inversely proportional to BMI (i.e., the more BAT, the lower the BMI)

Another study (link) found that in normal weight men BAT was more active after fasting than after a meal and that being exposed to cold increased its activity even more.

Last, another study (link) of the so-called 'skinny gene' SIRT2 which is activated by calorie restriction, and by a short (24 hour) fast in white and brown adipose tissues is also activated by cold exposure in brown adipose tissue. Activation of SIRT2 promotes fat burning and inhibits fat cells (adipocytes) from multiplying.

So, this is more evidence that fasting can help fat burning and keep the fat cells in check. Also, when we are feeling cold during our fasts perhaps we should remind ourselves that we may get better fat burning from the cold!

So would this be an argument in favor of a 24 hour fast? As it is now, I think I've morphed into doing 21 or 22 hour fasts, simply because if I don't eat during the day, I'm not hungry. 500 calories is plenty to satiate me at night.

More fascinating nerdy stuff, carorees, thank you!

I remember watching a Horizon programme in the 1970s about brown fat and a scene of two mice in a cold box, the fat one shivering in the corner, and the thin one running around happily.

It certainly doesn't feel to me as if fasting is switching on my internal radiators, but maybe I need to run around a bit more on my repair days? Hence squash on Thursday coming...

I saw the same programme - I have always had a low normal body temperature since childhood - if my temperature is 37 degrees, I am ill. This can be an indicator of low thyroid, apparently - but although this was tested over the years, the result was always within medically accepted parameters. I was diagnosed with low thyroid about 2 years ago, and reluctantly prescribed 50mg of thyroxine daily, the dose has never been increased, even though it does not seem to do much. I hate being cold, have been struggling to fast while it is cold, and if I get too cold for too long, I am physically ill, firstly with stomach issues, then with shaking and a real problem getting warm again. I would like an injection of Brown Fat, I am sure it would help!

I am fat and Auburn........ Is that close enough.


Sorry....

I am a 42 year old child! ( substitute child/man)

Caroline - do you have access to the full article in your second link above. The abstract is v limited in its description. If so can you please post it on here or if you think it's too big PM it to me.

Am interested to know more about BAT. Can you increase the number of your BAT cells (you can't with white fat cells after 16-18 yrs old) and if so how, or how do you relpenish the fat in BAT cells? How cold do you have to be to activate BAT metabolism, mild discomfort of core body temp <36? Questions, questions, too many questions..

It seems to be paywalled

I think it may be possible to increase BAT. I was looking at autophagy in adipose tissue and thought I saw something about BAT but I haven't had time to follow it up.

No worries, am digging elswhere on this subject too. thks

As ever Mark and his daily apple has a good write up on brown fat:

http://www.marksdailyapple.com/a-primal ... z2KIqx4IGB

Thanks for that skippy!

The methods required to create more brown fat sound rather daunting! Though, we hardly ever have the heating on at home and all winter I am cold! Especially on a fast day like today. We do have a rayburn cooker in the kitchen that is on all winter so the house is not actually freezing but it is not warm either. I guess I will have to learn to embrace the fact that my fingers are going numb along with my tummy being hungry as both mean that I might be activating the BAT.

Right, I'm off to do some exercise which will, I hope, warm me up, stop me feeling hungry and create some BAT into the bargain!

Another paper that shows you can create BAT through cold exposure. Brrrr....

Okay so this is why I am always cold on fast days!