The Art DeVany blog on paleo says that humans kick into a higher level of activity when they get hungry, because that is when need to be active and alert for seeking out the next food. So fasting = higher metabolism, according to that idea. It also fits in what people have been saying about higher energy and alacrity when fasting.

That's an agreeable statement. But most nutritionists and people would disagree with it.

Do you know why we get headaches at the end of the fast? I'm doing fasting for 24 hours now, every day, and I only started yesterday, but I got a bad headache at around 18 hours of fasting.

Headaches, hum I have no experience of fasting so I don't know. If I were trying fasting, I would not be deterred by a couple of initial experiences of headache, but if it persisted beyond that I would think something was wrong. Could it be a dehydration headache? I have never got into the habit of drinking the recommended eight 8-oz glasses of water per day, but one thing I do whenever I feel noticeable dry mouth or the beginnings of headache is to drink straight down about 16-oz of water. Is not always appealing but I think it works.

I would have to disagree with that logical conclusion also. I believe the higher activity levels may be the body's way of dealing with the absence of food, however, the body is also in conservation mode - blood vessels constrict, temperature is lowered, and of the energy available, the major life organs are being fed at the expense of other vital necessities (i.e., mentsruation in females will likely cease). Even the tiredest, most worn out person in the world will respond to adrenaline and the other hormones that kick in at this stage. Further, I would think that this state could only last so long before the organs start to revolt.

This is not to say that I think fasting is bad. I just think we should all be careful of the possible downside to all of this - the slowing of metabolism.

24 hours every day? Girl, you better eat something!

Capo & ProteusOne - One thing I wonder about though is the relative times at which the body starts to feel hungry and at which it starts to go into conservation mode. We modern westerners feel hungry after 12 hours without food. But people can last many weeks without food. So the question is does the conservation mode/slowing metabolism kick in when we first feel hungry, say within a day without food (the sorts of fasts being discussed here) or later.

I have been at plateaus throughout my life where eating 1,000 calories a day was sufficient for me to maintain being overweight. Of course, these plateaus always end at some point, but when you start factoring in possible other aspects such as insulin resistance, years of yo-yo dieting, age, etc., I believe there is ample evidence of a slow-down. Funny, I've always lost more weight eating more of the right kinds of calories, than by cutting them out. I still maintain that this is the "magical" benefit of the low-carb diets - ultimately, in the long run, fewer carbs are consumed, but not so few that your metabolism slows; therefore "tricking" your body in a sense into thinking it is not facing scarcity.

I think fasting may have other benefits, if taken in moderation, rather than effects on weightloss alone.

But this is only a 24hr fast. Menses are highly unlikely to cease because of eating 24hr on/off. Conservation/starvation mode are, I believe, blown way out of proportion by people in the West - it takes a lot less than 1200kcals per day and a very low BF% (much lower than the vast majority of Westerners) before real starvation/conservation mode kicks in, IMO.

It's going to take a heck of a lot more than a 24hr fast/feast cycle to cause any of the above (ceasing of menses, organs startng to revolt, etc.).

Also, you say that a slower metabolism is a 'downside' - actually, a slower metabolism is a good thing WRT life expectancy. If you read the Eades blog he points out that the majority of things that happen in so-called 'starvation mode' are good things.

There is a slow-down in conversion of thyroid T4 -> T3 when you are low calorie.

There are people here who are trying to lose weight, me being one of them. Any way that I can rev up my metabolism until I reach my desired goal would be good for me, and the lifespan payout most beneficial to me right now will likely come from losing weight as opposed to slowing my metabolism. Just like my coffee addiction, I'll worry about that next. I've got several more pounds to lose.

So, I am guilty of being a little centric here in my conversations about metabolism. Right now, I simply think that my weight issue "outweighs" any benefits I might derive from a slower metabolism.

Also, I got the impression that some here were fasting quite often (18-24 hrs, several times a week). I may be incorrect about that. I'm a scientist, so it will be interesting to see if anyone here trying to lose weight will just end up slowing their weightloss by fasting. Reasonable question.

And another thing... (there's always something, eh?): there are folks who eat too much (Camp gluttony); there are those who eat too much and then gag it back out of themselves (Camp Bulemia); there are those that compulsively undereat (Camp Anorexia); and there are those.... (and where was I going with this?). Oh, who's to say that one may be labeled a "mental illness" and not the other?

Not to do with diet, but to do with metabolic rate - cold water swimming can boost immune function and also metabolic rate. I now normally finish my showers with about 60 seconds of cold water, which maybe or not is enough cold exposure to trigger these effects, but I figure it cannot do any harm. It sounds uncomfortable but actually you do rapidly realise it's more psychological than physical discomfort, I hardly think about it now, I just hit the tap to cold at the end of my shower and spin around a bit and I am done. There's a huge difference between cold water swimming and a very short cold shower but maybe worth considering if you are exploring all avenues

http://www.wemjournal.org/wmsonline...ue=03&page=0191

Yes, they are - but they're eating every day.

So, for example, they'll fast from 6pm one day until 6pm the following day. They would then start eating again, and continue until 6pm the next day, when they would start over (fasting until 6pm the day after)... etc. So it's a feast/fast cycle of 24hrs/24hrs, and you get to eat every day.

On this and other boards (Firm YaYa's and LowCarbFriends) I visit I've noticed that many who strictly practice this have lost the last 10lbs that they've been struggling with - and they're not even eating strictly low-carb or counting calories.

I don't know if you've read the blog that Dr. Eades posted in late 2006, but if you haven't you should. There's a lot of comments on it and he replies to many. It's an interesting read.

Proteus, this is the little detail you seem to be forgetting. The 'natural' calorie reduction low carb eating causes (through less hunger) is far more likely to cause a slower metabolism than regular moderate fasts (up to 48 hrs, though I've never heard of anyone doing IF more than 24 hrs) with unrestricted calories in between.

The flip side of no slowing of metabolic rate is that you are much more likely to settle into serious bodyfat burning if you are not constantly feeding the energy furnace with external fuel - ie food with regular meals. And if you make the food you do eat low carb, you are much less likely to store excess calories as bodyfat.

The easiest way for you to discover that this metabolic slowdown idea from IF'ing is a furphy is to give it a go. Even after one week you will see the scales move better than they have on low carb alone.

But keep your eating low carb. Big high carb meals guarantee that you will store a lot of it as bodyfat. So even if you are burning a lot of bodyfat in the fast, you won't really be gaining anything.

I think you guys know what's best for you. I believe, however, that fasting on anything other than a very periodic basis is not the best thing for me to do at the moment. I agree that there may be some element of "settling" into a fat-burning mode, and I agree that only after one week I'd see "good" results on the scales. But I do not agree that this should be a mainstay for someone who still wants to lose 70 more lbs. I don't plan on making fasting a way of life once I reach my goal (and I will reach it ). Everything that I've read and experienced indicates that metabolism slows down in times of scarcity, and I believe this to be a logical extension of my trust in evolutionary principles. Do I believe everything I read? Certainly not! But when combined with experience and and testimonials of people I know, I'm likely to trust an idea until I'm ready to experiement more or face other logical reasonings.

So, give me the link to the Eades stuff. I'll check it out. The more a person knows...

Proteus, this is what I'm curious about. I've never read any evidence that scarcity over the kind of time frame we are talking about (up to 48 hrs) slows metabolic rate. Perhaps you could suggest where to find it?

And I'm glad you mentioned evolutionary principles, because it is beyond all doubt that humans would have spent the entire paleolithic IF'ing. It's probably why fatburning becomes a more signifigant metabolic pathway. Only the Neolithic transition introduced regular meals. How could that be a sensible (based on evolutionary principles) way to eat for optimal bodyfat regulation and health?

By all means wait until you are ready to experiment, but be clear with yourself that you are perhaps not using evolutionary logic at all .