Sunday, August 26, 2007

Intermittent Fasting - refuting the critique

I have written a little bit already about intermittent fasting (IF). I think interest in it arose most recently from those who were looking at the longevity benefits of calorie restriction. In animal models at least these benefits were also replicated through intermittent fasting, which seems to promote the same beneficial hormone drives.

There are variations on this idea. For example, the QOD diet has people eat every other day while the Warrior Diet promotes undereating all day with a feast at night.

I've read the Warrior Diet and it is a good read as an introduction. Fast 5 is another similar approach, written by a Doctor. The book is available for free from the Fast 5 Website and is also highly recommended and very good value (considering it is free). Their idea is that you can get the benefits of intermittent fasting from compressing all your eating into 5 hours a day they have it between 5pm and 10pm.

Interestingly this is how Hunter-Gatherers tend to eat. They go off and hunt for the day and have a big meal at night (if they are successful in the hunt). Loren Cordain talks about this in his Paleo Newsletter

Michael Eades also wrote about this approach in his blog recently which prompted a flurry on interest from the low carb community on the interweb. Then Mark Sisson also had a piece on this.

One of the commenters on that post pointed to a critique of IF by a guy called Alan Aragon.

His "Objective Look at Intermittent Fasting" is here.

Interestingly, Dr Herring who wrote Fast 5 has given a rebuttal to Aragon's criticisms on the Fast 5 yahoo group which is worth reading just from the perspective of seeing how there are always two sides to these discussions:

Although this piece is referenced, it has little integrity and exhibits lots of bias. For example, the author references #15 and 16 as examples of increased hunger when eating "a single meal." Those studies actually looked at the difference between breakfast served as one portion or spread over five,evenly spaced portions, after which the subjects ate lunch. The studies only looked at people over the course of 5.5 hours on 2 days. (One day they ate one way, the other day, the other way.) When the men in the study ate the breakfast in divided portions, they ate less lunch. (#15 studied lean males, #16 studied obese males).

References 17 and 18 are cited, saying basically that every-other-day fasting and once-a-day eating are impractical because people may not like it. The author does not include, for example, that in reference 18, the people in the study lost 4% of their fat mass in 22 days, their fat metabolism went up by 6 grams per day, and their resting metabolic rate, despite all "everyone" says about it dropping with fasting, did not change from baseline.

Reference 19 is an interpretation of other studies funded in part by the Breakfast Advisory Board, which is an agency of the State of Florida Department of Citrus. The Breakfast Advisory Board is now called the American Breakfast Council, even though it's an agency of the State of Florida created to promote orange juice sales. Another of the authors on the same paper, Judi Adams, is president of the Grain Foods Foundation and at the time was president of the Wheat Foods Council. It's no surprise that this interpretation of other studies came out "pro-breakfast."

Mr. Aragon spends a lot of time describing how hunger increases with decreasing meals, but disregards (a) that he's looking at a comparison of >3 meals a day to 3 meals a day and (b) his own statement that "hunger disappears" with fasting (which he calls "complete starvation" and then says it "is irrelevant.")

The next study he quotes (23) refers to people eating six meals a day. I don't see the meaning in including data from a six-meal-a-day study as evidence for or against intermittent fasting.

Mr. Aragon continues, saying reference 24 argues in favor of a post-fast breakfast. My reading of the article doesn't agree -- Layman is favoring more protein in breakfast for those who are eating breakfast and attempting to lose weight. Coincidentally, Layman's work was funded by Kraft Foods, the Cattlemen's Beef Board, and the National Cattlemen's Beef Association.

I could go on, but Aragon's article just isn't worth the time. It is a difficult endeavor to pick apart these sorts of scholarly-looking articles, and it takes a lot of time. When you do, you may come to a completely different conclusion than the author. There are parts of Aragon's article I agree with: "Intermittent Fasting Human Research – Interesting But Inconclusive." That is, we don't know all we need to know about it.

More study should be done on IF, and on longer-term studies than anything that's been done so far. Part of the problem is that much of the data describing fasting means a prolonged fast -- going without food for three or more days done as one single stretch, one single change interrupting a well-established pattern. IF is an established pattern and relies on adaptations over two months or more, so until we start studying people who are adapted to one form or another, we're not seeing the real changes that can happen.

The abundance of misinformation and misguided interpretation means one should be skeptical of ALL nutritional advice (including mine), and especially those who are trying to sell something. The best judge you have is your own body. If somebody's happy doing what they're doing, I see no reason for them to change to Fast-5 or IF or anything. If they're not, Fast-5 or some other variation of IF may be the tool they need to get where they want to be. As Aragon's reference #17 says,

"Although the consumption of 3 meals/d [per day] is the most common pattern of eating in industrialized countries, a scientific rationale for this meal frequency with respect to optimal health is lacking."

If you have any questions about other parts or statements in this article, please let me know and I'll add more detail.

Best wishes,



Alan said...

Hi Chris, I wrote a comment in response to Herring's bit about my article, here's the link, feel free to link this into your next blog entry:



Chris said...

Happy to Alan....

Next post coming up


Viagra said...

I eat only that I need, to me the best diet is this eat that you need and no more.