12 replies to this topic

[johnross47]

My wife and I have been looking at two days a week intermittent fasting as an option, particularly since we have just returned from an extended stay in the south of France and all the excesses that can imply. I've seen the BBC programme about it and read various posts here and elsewhere but I can't find any evidence that anyone has done the obvious study to determine the optimum calorie intakes.

Different people are recommending different levels, 500 600, 650, 800 etc. Has anybody actually done a proper comparison? Or have they just plumped for a number and tried it, found it worked and carried on.

There are lots of diet books and articles coming out around the idea now but many look dubious to me. Scottish Slimmers for example are pushing a diet involving large amounts of milk on diet days, plus salad/veg as you like, but passing that through cron-o-meter shows deficiencies that would take a lot of effort to rectify on the other days, or would require supplementation. Fine, but they don't say take vit B3 or whatever; they don't look at the issue at all.

So, does anyone know of any good research looking at these issues?

[ta5]

IF seems like a pretty bad idea.

Free' class='bbc_url' title='External link' rel='nofollow external'>http://pmid.us/21816219']Free Radic Biol Med. 2011 Oct 1;51(7):1454-60. doi: 10.1016/j.freeradbiomed.2011.07.006. Epub 2011 Jul 21.
Long-term intermittent feeding, but not caloric restriction, leads to redox imbalance, insulin receptor nitration, and glucose intolerance.

Calorie restriction is a dietary intervention known to improve redox state, glucose tolerance, and animal life span. Other interventions have been adopted as study models for caloric restriction, including nonsupplemented food restriction and intermittent, every-other-day feedings. We compared the short- and long-term effects of these interventions to ad libitum protocols and found that, although all restricted diets decrease body weight, intermittent feeding did not decrease intra-abdominal adiposity. Short-term calorie restriction and intermittent feeding presented similar results relative to glucose tolerance. Surprisingly, long-term intermittent feeding promoted glucose intolerance, without a loss in insulin receptor phosphorylation. Intermittent feeding substantially increased insulin receptor nitration in both intra-abdominal adipose tissue and muscle, a modification associated with receptor inactivation. All restricted diets enhanced nitric oxide synthase levels in the insulin-responsive adipose tissue and skeletal muscle. However, whereas calorie restriction improved tissue redox state, food restriction and intermittent feedings did not. In fact, long-term intermittent feeding resulted in largely enhanced tissue release of oxidants. Overall, our results show that restricted diets are significantly different in their effects on glucose tolerance and redox state when adopted long-term. Furthermore, we show that intermittent feeding can lead to oxidative insulin receptor inactivation and glucose intolerance.
PMID: 21816219

→ source (external link)

Edited by ta5, 30 December 2012 - 09:37 PM.

[johnross47]

Interesting!!! All the other references I've seen so far have been pretty positive but not overwhelmingly convincing, though I'm just plodding my non scientific way through one of the papers referenced on Wiki p which does seem to show mixed positive and negative effects.

[johnross47]

http://ajcn.nutritio.../4/981.full.pdf

[johnross47]

http://www.ncbi.nlm....8?dopt=Abstract

[DR01D]

I wouldn't be so quick to shoot down IF because of glucose problems. 2 CR members recently died from Pancreatic cancer which is a relatively rare disease.

Exhibit A)
Impaired glucose tolerance epidemic emerging amongst Calorie Restriction Society members

Obviously anyone who takes their diet to an extreme over long periods of time is asking for trouble. By that I mean ultra low calories, ultra low protein, mega doses of chronic fasting, etc. etc.

The smart choice is to eat a balanced, low calorie diet combined with a small eating window or moderate fasting. That's the diet our ancestors ate during 250,000 years of human evolution. It's a safe assumption that humans have genes optimized for that lifestyle.

Edited by DR01D, 31 December 2012 - 01:32 AM.

[johnross47]

I've seen a lot of mentions of the evolutionary aspects, which makes sense to a degree. I always have a bit of an issue with that approach because although humans evolved as hunter gatherers, it was a long time ago and there seems to be increasing evidence that evolution has continued to produce various adaptations in local populations everywhere. So most Europeans and some Africans can eat dairy, but many Chinese can't, etc. Has there been any evolutionary survival value in modern eating habits or are we still adapted to tolerate, if not enjoy, intermittent eating? As recently as 800 years ago, possibly even more recently, European eating patterns were radically different, with two main meals in the day and a longer fasting period following the main meal in mid to late afternoon. (at least for the aristocracy.....is the pattern for poor people known?)

It's quite possible that, given the broad tolerance of the human organism for sub-optimal diets, there has not been any profound evolutionary pressure and the optimum is still derived from the plains of Africa.

[DR01D]

You're correct that evolution never stops but most of human evolution took place when we were hunter gatherers. Modern humans have been around for roughly 250,000 years while farming took root over the last 10,000 years.

IMHO I don't see anything wrong with the 5/2 fasting diet. Eating low calories twice per week is sensible and not so different from the way humans ate for most of their existence. I wouldn't worry about one study. Studies get reversed all the time as science improves.

European eating patterns were radically different, with two main meals in the day and a longer fasting period following the main meal in mid to late afternoon.

I've found that eating that way is easy. Sometimes my wife and I eat a "mega lunch" which means dinner and lunch in one meal. We don't eat again until breakfast the next morning which is about 18 hours. The body hardly misses dinner. Maybe humans have genes that support this eating pattern because it's no problem at all.

I've tried skipping breakfast on numerous occasions and I felt miserable every time. I had trouble with concentration and I always got really hungry. It didn't seem natural to me on any level.

[johnross47]

I agree with that. If I only had one meal a day it would be breakfast. I have done the two meal bit a few times, unintentionally because we have had a huge lunch for some special occasion and I felt full till the next morning. Not a problem.

[johnross47]

This is interesting but the original question was about the different calorie levels proposed for different versions of IF diets. Is there any research to back up particular levels? Why should I choose 650 or 750 or whatever?

[DR01D]

I believe the Chicago study used 500 calories for women and 600 calories for men as a starting point for the 5/2 diet.

However I doubt that number is set in stone. To the best of my knowledge there hasn't been a single, large study on 5/2.

[johnross47]

That is what I suspected. A number was picked.......it worked, so they went along with it, but some other amounts might work better....if it remains a topical idea somebody might get round to the obvious trials.

[TheKidInside]

One or two days a week my girlfriend and I (I fast 16-18 hours daily) usually take a break from solid foods and concentrate on juicing BUT we utilize it to simply take in micronutrients. So, leafy greens, some ginger, some maca, cacao and flax powder and not too much calories. I feel "cleaner" and better with no negative side effects on my athletic performance, cognition nor anything else, really.