I wonder about the effects of prolonged, but not extreme dieting. If you lose weight by cutting calories to say 10% below TDEE every day for 6 months or a year or longer would that lower your metabolism. I’ve always expected that it would, but I wouldn’t be surprised if there isn’t any data on that, just because of the difficulty and expense of long term human diet studies. I consider it an advantage of intermittent fasting that you can meet or exceed your TDEE most of the time while still losing weight. I think the non-fast days might be necessary for avoiding the problem of slowed metabolism. But it’s just a conjecture as far as I know.

I had my last meal on Sat night at 7 pm . Today I have eaten 400 cals . I wasn’t going to eat again until tomorrow night Monday . is that too long? I have done this on my two fasting days . this is my first week xx

http://en.m.wikipedia.org/wiki/Starvation_response

I’ll agree with Micheal on this, however I do feel generation genetics play a role. If some of your recent ancestors have been through famine in childhood? I believe genes are sophisticated enough to pass on traits that slightly alter the rate we store fats. For instance some obese people continue to get larger and larger even unto a 1,000 lbs, while others will hover between 350-and 450 no matter how much and how often they eat. My opinion is this myth will be very difficult to eliminate because of generational variables.
Often discussed is the ease of losing the first 25lbs, but last 25 is more difficult from diet alone. There must be a reason for this? Yes?

Sorry SAMM, I have no idea what you mean by generational variables. If you mean that previous generations have experienced food shortages and we have not – well, yes, that has happened. But genes don’t have a memory a la “oh, your mother went through wartime rationing, you should be prepared – here, get fat”. They do pass on “traits”, that is what genes do, they are our ancestral information on how the body should function; however, changing these traits takes a long time and does not happen as a quick responds to your parents’ living conditions.

One of the reasons why weight loss slows down is that with diminishing waist lines the BMR changes. It simply takes less energy to get out of bed when you weigh 60 kg than to lob 120 kg off the bed. It takes more energy to move blood around a 120 kg body than around one half that size.
On long-term calorie restricted diets the body realises that you have lost weight and will reduce BMR to avoid starvation. Michael mentioned this in his post, this is the metabolic adaptation occurring after months of significant calorie restriction.
I am not aware of studies that look at BMR changes after long periods of intermittent fasting, for example after 6 or 12 months on the 5:2 diet. There are people like Brad Pilon who claim that intermittent fasting fools the body into believing that there is no overall calorie restriction and the metabolic adaptation does not occur even after significant weight loss and years of intermittent fasting.

http://www.nature.com/ejhg/journal/v15/n7/full/5201832a.html

I probably won’t find the video I’m think of , but may find reference pointing in this direction.

@marielaem – re swapping cigarettes for e-cigs and gaining weight (I apologise if someone else has remarked upon this in this thread): My mum did the same a good few months ago when she was on a roll of losing weight and exercising. Her weight-loss stalled and she actually gained a few pounds….in complete disbelief she told me about it and I researched my way to an answer: Cigarettes apparently increase your metabolism, so without them presumably your metabolism would decrease – thus the weight gain. Luckily not starvation mode. (Obviously I might be wrong as I’m not an expert, but that’s the answer I found. And it makes sense!) Just keep doing what you’re doing and have a little patience. (And by the by, my mum is losing weight again!) Alex xxx

Hi SAMM,
You can watch the BBC Horizon documentary that features studies here on Epigenetics ‘THE GHOST IN YOUR GENES’: http://www.youtube.com/watch?v=fMxgkSgZoJs
In the documentary one such study by Marcus Pembrey, a Professor of Clinical Genetics at the Institute of Child Health in London, in collaboration with Swedish researcher Lars Olov Bygren was particulary interesting. They studied the parish registries of births and deaths in a remote village in Sweden, Överkalix, including detailed harvest records and showed evidence of an environmental effect being passed down through grandparents who were subject to a famine at critical times.

Thank you. I am battling on! I have severely restricted carbs to see how that goes, and it seems to be working – I got to the point where I had gained 10lbs. I have now dropped 4. I have also cut back on the vaping a bit. I am still walking, fasting and going to the gym.

I haven’t found the fasting hard at all – the hard thing for me has been to be fasting, exercising etc etc and still to see the weight increase, especially as the 5:2 was working so wonderfully well for me before I gave up smoking. I did the 4:3 last week, and when I weighed I had gained another 4 lbs. I felt like crying when I saw that I was getting back up to my pre-5:2 weight.

I’m almost doing Atkins Phase 1 now! Psychologically, it has been a real boost to see the scales go down a little instead of up.

I understand that the metabolism increases during an intermittent fast yet I was struggling to argue the point with a colleague when she insisted that lost of water is required to tell the body not to “store” while you are fasting. She insisted that you need more than usual whole fasting, while I argued that if you are eliminating clear fluid regularly, then that is enough water, and that happens for me without drinking any more than I normally would (2-3l a day).

If the metabolism is higher, does that mean that your body is burning, not storing the food you eat?

Michael,

Regarding your original post you may be interested in this link on Pubmed that Susan Jebb sent to me recently:http://www.ncbi.nlm.nih.gov/pubmed/22540251

Hall describes an adaptation scenario where thermogenesis is reduced (organs stop producing as much heat) during weight loss. He did not see a corresponding increase during weight gain though!

Can this effect be cumulative though? Meaning your body would switch this on after a short time dieting because many weight loss attempts had been made before? An increased response to famine as time goes by?

Regards,
Mike.