Tuesday, March 04, 2008

Bad Arguments for Intermittent Fasting

I've been reading a bit on "intermittent fasting," which is basically the notion that your health might improve from occasionally skipping a meal or two (or a day of eating). I'm agnostic on such fasting, and one reason is that I keep seeing this argument:
We modern humans have become acculturated to the three square meals per day regimen. Animals in the wild, particularly carnivorous animals, don’t eat thrice per day; they eat when they make a kill. I would imagine that Paleolithic man did the same. If I had to make an intelligent guess, I would say that Paleolithic man probably ate once per day or maybe even twice every three days. In data gathered from humans still living in non-Westernized cultures in the last century, it appears that they would gorge after a kill and sleep and lay around doing not much of anything for the next day or so. When these folks got hungry, they went out and hunted and started the cycle again.

If you buy into the idea that the Paleolithic diet is the optimal diet for us today because it is the diet we were molded by the forces of natural selection to perform best on, then you should probably also buy into the idea that a meal timing schedule more like that of Paleolithic mean would provide benefit as well.
The bolded phrase strikes me as especially uncertain. The Paleolithic diet was obviously something that humanity was able to survive, in the sense that it didn't totally kill us off, but that doesn't mean that we evolved to perform best on such a diet. Think of it this way: We may have evolved to be able to last for three days without water, but that in no way implies that it is ideal for us to try to drink as little as possible. (I wonder when we'll start seeing "intermittent water" diets purporting to mimic the experience of the Paleolithic hunter who ran out of water and spent three days looking for a new supply.)


Blogger Brad Pilon said...

Hi Stuart,

Interesting post. I'd like to point out that not all proponents of IF are also proponents of the whole Paleo argument.

I wrote Eat Stop Eat based on current and available research, and under the hypothesis that it was simpler an easier way to cut calories with some metabolic benefits.

In all honesty without "googling" it, I couldn't even tell you when the paleolithic era began or ended.

Brad Pilon

4:58 PM  
Blogger Stuart Buck said...

Fair enough -- there may be some good arguments for intermittent fasting. My only concern is that some people seem to think that if Paleolithic humans did X, that must mean that X is actually the best thing for us to do now. Not necessarily -- Paleolithic humans might have eaten vegetables only for a few months a year, but that's just because they didn't have good refrigeration or canning methods, and it doesn't mean that carrots are bad for you in February.

11:17 AM  
Blogger Tully said...

My only concern is that some people seem to think that if Paleolithic humans did X, that must mean that X is actually the best thing for us to do now.

Er, they lose me at the "dying of old age and decripitude at 38" thing.

9:34 PM  
Blogger Scott Kustes said...

Nice post Stuart. You are correct that just because our ancestors did something doesn't make it a good reason to do it, de facto. However, I think the key point is looking to ancestral ways of living and using them as logical starting points for experimentation. Intermittent Fasting is showing lots of clinical promise with benefits ranging from improved insulin sensitivity to improved resistance of healthy cells to chemotherapy (not to mention decreased cell proliferation rates, i.e., lower cancer risk). I actually have a series going on my blog right now regarding the physiological effects of Intermittent Fasting...Part 1 starts here.

Tully, that is a fallacious argument. 35 (or 38 or whatever number is routinely used) is an average life expectancy factoring in a VERY high infant mortality rate and the fact that many young men die of wounds that we can deal with at the hospital. I wrote a post on this some time ago: Paleolithic Longevity. Fact of the matter is that those that avoid traumatic death live very well into old age with few of the illnesses exhibited by Western society.

Scott Kustes
Modern Forager

10:49 AM  
Blogger Dtktv said...

The title of this post is inaccurate. You only provide one example of a bad argument. "A Single Bad Argument for the Paleolithic Diet" would have been appropos.

2:45 AM  
Blogger powersam said...

Actually the argument behind the Paleo diet is more that as the foods available around that time had been available for so long, our digestive systems had time to evolve to accomodate them. The same cannot be said for recent additions such as wheat and dairy.

The only restrictions on the Paleo diet are really to eat foods that would have been available to humans back then or their modern components (cow instead of mammoth etc).

Not really about only eating veggies at certain times of year etc. More about just making sure what you eat is what the human digestive system had time to evolve to deal with.

7:11 PM  

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