The FastDay Forum

Geodesic-

1) Underweight is BMI below 18.5 - which does not apply to Franglaise or me

2) I have lost 13 lbs on this diet but do not intend to lose anymore - 5 ft 10in and 9 stone 12 sounds about right for a 62-year-old who is reasonably active.

3) I do not seem to have 0% body fat - the usual calculation (can be found on this forum) suggests 21.6%

4) I have been an athlete, although not spectacularly, having run a marathon in 2h 54m, 100 km in 12 hrs and done the Bob Graham round of the Lake District in my time. I still do parkrun every Saturday morning.

5) I cannot comprehend your comment that fasting can achieve an ideal bodyweight. Bobby Sands and others died by fasting. What controlled fasting can do is reset your appetite, retrain bad eating habits and allow sufficient time between meals that insulin etc can be reduced to normal levels.

Why are you so concerned about Franglaise and I who clearly wish to be as light as reasonably possible without getting into difficulties? We believe there will be a health benefit, we might be wrong but we have done ourselves no harm getting to where we are and trying to maintain this happy state. My most recent blood test was very satisfactory for cholesterol etc, my doctor has no problems with my weight.

1) "Underweight" is not some arbitrary mathematical formula defined by some ludicrous definition like 18.5 x weight (kgs)/height (m)^2. Your body has an ideal weight which it will try to attain after you fast and start eating again (assuming you lose enough to go below that ideal weight) and then don't overfeed it afterwards. Yours may equate to 17 x weight (kgs)/height (m)^2 or 21 x weight (kgs)/height (m)^2 - only you can find this out.

2) Doesn't sound unreasonable to me either BUT your body may consider this underweight and you may struggle to maintain it, assuming you are healthy which it sounds like you are.

3) I wasn't suggesting what your level of body fat is, but merely pointing out that your comment suggested a desire to be carrying around as little fat as possible. My point was that this may not be a heathly aim if taken to extremes.

4) I'm pleased that you have been fortunate in living an active life and that you continue to do so.

5) For someone who is apparently quite knowledgeable on fasting, I'm amazed that you would cite an example of soemone on hunger strike deliberately killing themselves - he carried his fast into starvation. Fasting and starvation are two completely different things.

As to your last paragraph, what you choose to do is of course up to you. But on what are you basing your assertion that there will be a health benefit in having one or other BMI - why is 18.5 "OK" but (presumably) 17.0 or 20.0 will not be? Are you not simply adopting an arbitrary standard number which cannot possibly have any real meaning for you personally?

Fasting is not feeding/eating. Continue it long enough and you starve (which means die). May I ask what your aim is in fasting, and how you will assess what your ideal weight will be, given that it will not be an arbitrary figure? I know I operate well at 10 stone 4 lbs, I had hoped to test 10 stone exactly but found myself accidentally where I am now. Maybe this is not my ideal but why put 4 lbs of fat back on until I get some clue that I have gone too far - and that evidence will either come from blood tests, diminishing performances or starting to become vulnerable to minor illnesses. Having kept reasonably cool this time, would you please stop trying to convince me that I am doing something arbitrarily wrong with my body and health? Cheers...

Ok, from what you've said the most likely explanation is that the well known reduction in thyroid function with fasting persists into the feeding phase resulting in weight gain. Probably the prolonged fast does seem to reset something there seems to be evidence that both overweight and underweight people benefit from fasting. Very interesting!

The theory is that if you are underweight despite eating heartily, then there is something wrong with your digestive system, and in fact you are not digesting your food properly. Advocates of fasting believe that a fast in this condition can enable repair of the system so that when eating is resumed the body builds back up a normal weight and with a repaired "normal" digestive system. It sounds counter-intuitive perhaps, but even underweight people have a reserve on which they will live quite happily whilst fasting, although clearly their endurance will be less than those who start a fast overweight before their natural hunger returns.

Of course plenty of healthy people are quite happy to be "underweight" by conventional standards and so this is not an issue for them. But there are also many others who perhaps do not feel that healthy and would love to gain weight and look and feel "normal" in their eyes.

Fasting is not feeding/eating. Continue the it long enough and you starve (which means die). May I ask what your aim is in fasting, and how you will assess what your ideal weight will be, given that it will not be an arbitrary figure? I know I operate well at 10 stone 4 lbs, I had hoped to test 10 stone exactly but found myself accidentally where I am now. Maybe this is not my ideal but why put 4 lbs of fat back on until I get some clue that I have gone too far - and that evidence will either come from blood tests, diminishing performances or starting to become vulnerable to minor illnesses. Having kept reasonably cool this time, would you please stop trying to convince me that I am doing something arbitrarily wrong with my body and health? Cheers...

OK Pete, but most texts on not eating distinguish between a fasting phase and a starvation phase. The two phases are characterised by the extent to which the body uses up its own tissues and the various changes in measurable body parameters such as blood pressure and temperature. In fasting the body uses its fat reserves from body fat, muscle fat, liver fat, etc (i.e. what they were designed to be used for when there was no food). The brain, heart, spinal cord and muscles are kept intact (indeed enhanced) such that you can run after and outwit your prey in order to feed again. Starvation occurs only after your reserves are used up and then the body is forced to consume its vital organs as well.

In terms of myself, I'm obviously well away from an ideal weight and will probably require several fasts to achieve that weight. I'm new to this but have done quite a bit of reading on it (unlike many on here it would seem) and so I'm assuming that if/when I do get down to a weight approaching my ideal weight I'll be able to tell what that is from how I feel and my lifestyle at the time - it would seem reasonable to use statistical guidance on this as a ball-park figure as an initial aiming point.

I'm not in any way saying that you are doing anything "wrong" - that is for you to decide. All I was saying is that if you are trying to lose weight by employing fasting (as you seem to be), then you may find that fasting leads you towards a higher weight once you resume eating. Obviously if you starve yourself to death, you can achieve well below statistical norms of underweight before you expire - what I'm saying is that your body's idea of the weight it functions best at may not agree with yours, which seems to be an arbitrary BMI of 18.5.

I read all your comments and I although I don't have any scientific knowledge on the subject I pretty much understand what Geodesic says. If I wanted to oversimplify, I would say that:
Since fasting is a procedure possibly full of healthy benefits and has helped many people return to a healthy body condition, why should we consider that it will definitely lead to weight loss? Assuming that one's weight is lower than it should be (not according to BMI, but according to the body's standards) then if fasting is supposed to do all good, it could possibly return the body to its ideal weight.

Geodesic - yet again you quote this figure of 18.5 BMI. Looks at my stats, read my fasting history elsewhere, look at my progress chart - my BMI is currently 19.6 and I am following a maintenance procedure of my own devising (fast 2 days a week but not restricting calories - ie skipping breakfast and eating sensibly) to obtain the benefits of reduced IGF, inflammation etc per Dr M's book - I am patently not trying to lose any more fat, and did not originally intend to lose this much. It just happens that I have and feel good as a result. The experiment has been a success, the next thing is to cut out all grains and possibly revert to occasional meat after 25 years of being a fish-eating vegetarian. Do you have any opinions on this?

I have to say I am sceptical about this supposed effect of fasting (that it moves the body to an 'ideal weight' whether up or down). And in any case does our 5:2 way of eating, which we call fasting but isn't really, have this type of effect (if it exists)? I see no evidence of it in our Tracker data here.

And if the body has an idea of our 'ideal weight' it is not necessarily the right idea.

Regardless of what idea the body may (or may not) have, intermittent fasting provides a way that we can control our own weight - for life. It is a regular and limited intervention that, as most of us already know, allows us to lose weight in a managed way and, suitably tweaked, should enable us to maintain it too, at whatever weight/BMI we choose.

You may well be sceptical about it Dominic, but that's just because you are ignorant of the actual cases where people were underweight but that have been "cured" by fasting. I've got no idea whether Shelton actually observed these cases or not - you seem to be suggesting he made them up. He may have done, although I'm not sure what his motive would have been. Have you read any of the works of people who have supervised many fasts?

Geodesic - yet again you quote this figure of 18.5 BMI. Looks at my stats, read my fasting history elsewhere, look at my progress chart - my BMI is currently 19.6 and I am following a maintenance procedure of my own devising (fast 2 days a week but not restricting calories - ie skipping breakfast and eating sensibly) to obtain the benefits of reduced IGF, inflammation etc per Dr M's book - I am patently not trying to lose any more fat, and did not originally intend to lose this much. It just happens that I have and feel good as a result. The experiment has been a success, the next thing is to cut out all grains and possibly revert to occasional meat after 25 years of being a fish-eating vegetarian. Do you have any opinions on this?

Hi Pete, sorry if I have misinterpreted your goal - I had formed the impression that you viewed all fat as excess weight you didn't need. If you feel good then great. Out of interest (and in no way critising your free choice to do whatever you want), can I ask why are you now contemplating cutting out all grains and reintroducing meat after 25 years - what are your anticipated benefits of doing this?

I'm looking to extend the life of my hip joints and reducing inflammation. There is a strong feeling online that grains are a big mistake, maybe other carbohydrates as well but you have to eat something and chips are a good source of fat. Meat has just got a clean bill of health from the recently-quoted study so maybe it would supply some nutrients which I might currently be short of. Similarly saturated fat needs experimenting with but for now I am settling for coconut derivatives (I always hated fatty meat).

Pete, I hope that you have asked your rheumatologist about all those things...

Sorry, but why do you people who are below BMI=20 WANT to be underweight?

Fasting will never help you do this. Fasting will propel you towards a normal weight, which means if you are below this, you will put on weight. Doh!

I've been away for the week-end and have just seen this. Fasting did help me lose weight - I started with a BMI of 21 and am now 19. 19 isn't underweight and I could probably lost a few more kgs and still look OK. I like being slim and feel a lot healthier than I did with a BMI of 21. It's a personal choice.
BTW in case anyone is interested last week I did one fast day and one day where I didn't eat until the evening but in the evening ate around 1200 calories. So I think this is what is needed for my maintenance in future.

I tried 6:1 also for a week but put on weightly slightly so went back to 2 days which I will continue until I fit into a size 12 dress, hopefully, then I will drop to it again.

Susan - glad to see you have regained control, I seem to have managed to do the same by a similar process of delayed meals and sensible eating, no snacks.

Geodesic seems to have upset you less than he did me!

TML13 - I have osteoarthritis (wear-and-tear, if you believe that theory) in my hip joints, no sign of rheumatoid arthritis. My doctor is aware of my fasting experiments, my physio has advised me to stop running and get a bike for exercise, next stop is hip replacements when I can't get upstairs any more. What would a physio know about diet? Mark Sisson is an example of someone who successfully changed from high-carb to Primal eating after suffering from joint problems as a younger man doing lots of running. I reckon it is worth a try!

Hi Pete
I actually had a few days with no chocolate at all and that probably helped!
How much weight you choose to lose is a very personal decision. I've never been overweight according to the BMI scale, except when I was pregnant. At my heaviest my BMI was 23.4, I was a size 12/14 and always felt 'big'. When I lost 10kgs I kept my weight stable for 3 years so I know your body doesn't have an 'ideal weight'. I don't want to lose any more weight now and I'm determind to keep stable and fasting one and a half days a week will work, I'm sure. As long as I don't overeat or oversnack on other days!
I think that cycling would be a lot better for you and your joints. I know a few people with ruined knees because of running and cycling is a lot kinder on your joints.