Saturday, November 19, 2011

Linoleic Acid, Fat Rats In Labs, and Fat Humans

Stephen Guyenet recently posted:
"...High fat diets, particularly in combination with refined starches and sugars, were among the most effective. The composition of these diets has been refined since then, and modern "purified" high-fat diets reliably induce obesity in susceptible strains of rodents. The most commonly used diet is Research Diets D12492, which is 60% fat by calories, and composed mostly of lard, soybean oil, casein, maltodextrin, sucrose and cellulose (7). It tastes kind of like raw cookie dough, and the rats are crazy about it."
Turns out a whole big chunk of science has been drawing faulty conclusions:
"...I got an email today from Dr. Matthew Ricci, the Vice-President and Research Director of Research Diets, the company that produces the infamous 60% fat, lard-based rodent diet D12492. I've written about this diet before. The company had previously been using the USDA database to determine the diet's fatty acid profile, but recently had it directly analyzed, knowing that the fatty acid profile of lard can vary according to what the pigs are fed.

"It turns out that the diet obtains 32% of its fat from PUFA instead of the previously reported 17%. The ratio of omega-6 linoleic acid to omega-3 linolenic acid had been previously reported as 7.8 but is actually 14...."
Whoops.  Chris Masterjohn compliments Research Diets on their transparency, which compliment they are due. However, Research Diets made a big mistake.  To paraphrase a line from Animal House, "They f---ed up, they trusted the Federal Government."  Obviously the USDA is not a reliable source of nutritional information.

The following is from one of several emails I sent to Stephan Guyenet in April 2010, shortly after I fixed my diet (and contributed $100 to support his blogging efforts):
"One more update.  I've been going through your site and it occurred to me that some of the other effects I've seen might be of interest.

"We have a candy bowl in the office.  Once of the first things I noticed after dropping n-6 from my diet was that I was no longer craving starch and sugar.  I haven't hit the candy bowl in 3+ weeks.  Didn't feel a need to.  My wife also noticed after not eating n-6 that she was no longer craving starch (and this has been a big problem for her).

"I didn't start craving fat for 3-4 days after making the change, and had almost no starch or sugar in the interim...

"I know you stress cutting starch[*] more than n-6 in your thinking.  I didn't want to change too many variables at once in my experiment, but since I don't eat processed starch or sugar, I figured removing the n-6 was the more significant change to make.

"It makes me wonder if there might be a mechanism linking the two..."
This sounds a lot like what happens to the rats.  I think Stephan may want to reconsider this post:
"As my knowledge of obesity and metabolism has expanded, I feel the evidence behind the hypothesis that seed oils (corn, soybean, etc.) promote obesity due to their linoleic acid (omega-6 fat) content has largely collapsed. "
I was very suprised when he posted it, as his previous position coincided perfectly with my experience as stated above.  It also turns out that the research he now quotes in support of the problematic food reward hypothesis also supports the position he's abandoned, given this updated information on the composition of the diets he cites.

Stephan may have reconsidered his position on seed oils, but I haven't.  I still avoid them like the plague, as they had a clear effect on me once I stopped eating them.

If you want to "reliably" induce obesity in humans or rats, feed them high amounts of linoleic acid**.

* Stephan corrected me about his thinking on starch he's basically OK with it.  And I think he's likely correct, so long as you're not eating large amounts of linoleic acid.

** Your results may vary. :)

P.S.  Chris Masterjohn posted a follow-up at the Weston A. Price Foundation website: Good Lard, Bad Lard.

One other thought: my sure-fire test to find out what chips are fried in is to start eating them.  With chips fried in olive oil or animal fat, I eat a few, and then move on.  With chips that are fried in seed oils, you eat the quantity presented to you, and then you want more.  This has been reliable enough that I've been able to detect when the staff at a restaurant gives me bad information about the constitution of the chips that are served.

P.P.S. "Dietary Linoleic Acid Elevates Endogenous 2-AG and Anandamide and Induces Obesity"