The FastDay Forum

Why does fasting make you so ruddy cold?

Well you do live in England

It's weird!! I like to think that I'm burning more cals if I'm cold?! Although I do think some warmer weather would help~ I can't believe that they're currently forecasting snow in Devon!!!

Could it perhaps be the body trying to conserve energy?

I am not fasting today and I am freezing!

I live in Australia and its just starting to cool where I am .Only its just starting autumn weather really and I find I'm colder even on warmer days than before I think it has something to do with reducing cards etc or not producing heat by digesting food just giving your body a break, maybe a nerdy type will be along soon to spread more light on it for you

Yeah we need some nerds.

Just to emphasise: this has nothing to do with the weather for me. I am significantly more colder on fast days. It begins a few hours into the fast. And lasts right until the fast ends.

*goes to fill hot water bottle*

I haven't worked out to link a thread from another topic but here is a quote from carorees that helped me

Digesting food takes energy so you generate some heat...it's called the thermogenic effect of food. It's the reason why people claim breakfast kickstarts your metabolism...it doesn't, yes your metabolic rate is slightly raised due to the energy needed to digest the food but of course the food provides more energy than it takes to digest. Anyway, the lack of food is why we feel cold on fast days.

However, feeling cold and fasting may activate brown adipose tissue which generates heat (that's it's function) and also burns up calories. People with more brown fat tend to be thinner. Cold exposure can actually increase the amount of brown fat. So it's good to feel cold!

Interestingly, I feel less cold on fast days than I used to, so perhaps I've now got a bit more brown fat!

I hope this help until a nerdy type can help out more

I haven't worked out to link a thread from another topic but here is a quote from carorees that helped me

Digesting food takes energy so you generate some heat...it's called the thermogenic effect of food. It's the reason why people claim breakfast kickstarts your metabolism...it doesn't, yes your metabolic rate is slightly raised due to the energy needed to digest the food but of course the food provides more energy than it takes to digest. Anyway, the lack of food is why we feel cold on fast days.

However, feeling cold and fasting may activate brown adipose tissue which generates heat (that's it's function) and also burns up calories. People with more brown fat tend to be thinner. Cold exposure can actually increase the amount of brown fat. So it's good to feel cold!

Interestingly, I feel less cold on fast days than I used to, so perhaps I've now got a bit more brown fat!

I hope this help until a nerdy type can help out more

Wow fascinating! Thank you for sharing.

I hope carorees will see this thread. I'd be interested to read some sources for her facts.

Well trying to class myself as a nerdy type...

Some info on dietary-induced thermogenesis (DIT) is on Wikipedia. This is basically the extra energy used to process the food you eat, not all of this is heat but presumably some of it is, hence when you eat you are warmer. Interesting that some foods require more energy (and therefore probably generate more heat) than others - processed foods predictably require less DIT (per calorie). The best foodtype for DIT is protein, in fact this is reckoned to be the reason why protein promotes satiety i.e. you feel more full - see 2004 study here.

Turning to brown adipose tissue (BAT), here is a recent study:

It is now apparent that potentially every human possesses BAT, it can be rapidly activated by cold exposure, the amount decreases with age and body mass index, and it is more likely to be detected in female than male patients. There is, however, considerable variation in potential BAT function which adds to the difficulty in assessing its potential role in overall energy balance regulation.

See sections 11 and 12 in particular.

In fact scientists in Cambridge recently (2012) identified a specific protein called - romantically - BMP8B which activates BAT, at least in mice. You might be pleased to hear that alcohol also activates BAT for humans, but of course none of those scientific killjoys is recommending it...

If you are 'lucky' enough to have plenty of active BAT it can help you keep warm in the cold and lose weight - and eating chilli peppers might help activate it - see here. There is a now special type of sweet pepper (CH-19) which produces the capsinoids that can activate BAT, and you can get it in pill form as 'Capsiate Natura', but only I think in the USA and then only from licensed healthcare professionals.

If you don't have much active BAT (clue: you get really cold on fast days!), you can fall back on these strategies on a fast day:

1. Wrap up a bit warmer
2. Take some exercise
3. Eat more protein (out of your 500/600 cals)

On a personal note, I used to find I got quite cold on fast days, but haven't noticed this for the last couple of months. Don't know whether this is some sort of metabolic adaptation or just that the weather has been slightly less bad recently in UK...

I'm one of those people who is ALWAYS cold, and I live with someone who refuses even to consider putting the heat back on (we're in southern England). The temperature reading on our freezer door is constantly at 12C. I couldn't bear the thought of fasting on days when I am working at home - I'm cold now, fasting in my office, but I would be a shivering wreck if I tried it at home today. When I'm really unbearably cold at home I get on the exercise bike for a good 30-45 minutes and I'm always nice and warm by the end.

I'm always cold on fast days, not helped by the rubbish English weather as its only 7 degrees here this afternoon and I've spent 30 minutes standing on the school playground in the rain. One of my old bosses used to say if you want to loose weight turn the thermostat down a couple of degrees the cold will make you burn it off, seems like he was on to a good thing.

For me the feeling cold on low calorie days is really the main downside to this otherwise brill diet. The explanations given above make sense. I try to deal with it by having lots of hot green tea and dreaming of warmer climes!

[carorees]

I haven't worked out to link a thread from another topic but here is a quote from carorees that helped me

Digesting food takes energy so you generate some heat...it's called the thermogenic effect of food. It's the reason why people claim breakfast kickstarts your metabolism...it doesn't, yes your metabolic rate is slightly raised due to the energy needed to digest the food but of course the food provides more energy than it takes to digest. Anyway, the lack of food is why we feel cold on fast days.

However, feeling cold and fasting may activate brown adipose tissue which generates heat (that's it's function) and also burns up calories. People with more brown fat tend to be thinner. Cold exposure can actually increase the amount of brown fat. So it's good to feel cold!

Interestingly, I feel less cold on fast days than I used to, so perhaps I've now got a bit more brown fat!

I hope this help until a nerdy type can help out more

Wow fascinating! Thank you for sharing.

I hope carorees will see this thread. I'd be interested to read some sources for her facts.

Here are some of the sources:

Some of the many studies on the thermogenic effects of food: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC524030/
http://www.ncbi.nlm.nih.gov/pubmed/10545669
http://www.ncbi.nlm.nih.gov/pubmed/17463294
http://www.ncbi.nlm.nih.gov/pubmed/3095110


Brown fat is activated by cold: viewtopic.php?f=10&t=390&p=8885 (several papers referenced)

Its nothing to do with fasting - I've been on a full on feed day today and I'm shivering - Its unseasonanably cold.