Low-fat diets better at depleting Linoleic Acid?

Another piece of the puzzle?

H/t to Tucker Goodrich for this excellent 1971 study in pigs.

a fat pig, gorging on soybeans and corn

Great, I was just about to have a lazy Saturday evening when Tucker Goodrich sent me this study.

I got so excited that I immediately abandoned all my plans (of doing nothing) and dove into it. Got me quite fired up about HCLFLP.

Today is day 27/30 of the Honey Diet and, after reading this study, I’m committed to doing another month of HCLFLP right after.

A Study in Pink

This is one of those old (1971) studies that just warms the heart. The researchers asked a basic question: how does feed content influence the linoleic acid level of pig fat?

Then they set up an excellent study design that tests every conceivable variation. All this in 8 pages with a handful of easy to read tables explaining everything. Why aren’t studies done like this any more?

If you’re not familiar, I believe that excess dietary linoleic acid (omega-6 PUFA) intake is the root cause of the modern epidemic of diabetes, obesity, and heart disease.

To clarify, the researchers in this study don’t seem to think linoleic acid is bad. They confidently claim that saturated fat causes heart disease, and they explicitly mention that some cuisines prefer the runny, oily fat of highly-polyunsaturated pig fat from pigs fed soybean & corn oil.

Study design: a perfect circle matrix

The pigs are put on 3 base diets: sugar, corn, and molasses.

Each of these is then supplemented with either 0% fat, 10% fat, or 20% fat. (Exceptions: the sugar diet wouldn’t hold 20% fat, so they left that out. And the molasses diet has 5% added fat, not 0%, for some reason.)

For one arm of each of these they used beef tallow, which is very low in linoleic acid (1-3%). For the other, they used soybean oil, which is very high (~56%).

In the above table you can see the diet composition:

• Sugar diet: 0% fat kcal w/o added fat

• Corn diet: 4% fat kcal w/o added fat, and it’s 57% linoleic acid (corn is VERY high in LA)

• Molasses diet: 16% fat kcal because the base here is 5% added fat for some reason

• Added soybean oil & the base corn diet are 56-57% LA, whereas the tallow numbers (in parentheses) are 4% LA in sugar & molasses diets, and 5/7% in corn diets (since corn is already high in PUFA)

Now let’s look at the fatty acid composition of the pig fat at time of slaughter. They actually tested 3 different fat tissues. The overall levels vary quite a bit between then, but the main findings are similar.

You can see that the lowest LA numbers by far are in the 100% sugar feed (3.7% LA) and sugar + tallow feed (3.1% LA).

All the “oil” (=soybean oil) diets are very high in LA, reaching from 16-47%.

Interestingly, the 100% corn fed pigs, with no added oil, already had 14.9% LA in their adipose tissue. That means that just eating lots of corn, in absence of any “seed oil” shenanigans, is already enough to significantly PUFA you up.

Another insight: in diets already containing significant LA, like corn & molasses diet, adding more tallow REDUCED the LA% in the pigs’ adipose tissue.

So far, this all makes sense: eating linoleic acid will make you store linoleic acid. Even the little bit of it in corn is enough to significantly PUFA you up.

Pork, chicken, and other meat from monogastric animals will quite literally be made of seed oils when you feed them seed oils.

Feeding them beef tallow makes them safe (if not eating corn) or at least slightly improve the fatty acid profile (if eating corn).

Follow up

But then the researchers had another question: what if the LA% of the feed was held constant, but the total fat content of the diets was varied?

They set out to design a follow up study:

• 2 base diets (bagasse & wheat fiber)

• 5/10/20% added fat

• All fat was of the same composition, containing almost exactly 16% linoleic acid

The point was: we know that increasing the LA% will lead to higher adipose LA%. But what about constant LA%, yet higher absolute LA content via higher total fat content?

Let’s take a look at the results:

Well, I’ll be danged!

The higher total fat (and therefore higher absolute linoleic acid) diets produced significantly more linoleic acid in the pigs’ fat.

The differences seem to vary between different tissue types. In the follow up, they only tested 2 tissue types: backfat and longissimus muscle.

• Backfat: linoleic acid % ranged from 15.2-22.5% for the bagasse feed, and 15.7-20.9% for the wheat feed.

• Longissimus: 7.5-19.8% for the bagasse feed, 7.4-17.3% for the wheat feed.

The difference is quite astonishing, especially in the muscle fat: 2.6x higher LA content just from a higher total-fat/total-LA diet!

Implications for PUFA-depleters

Anecdotally, this fits in well with the results from r/SaturatedFat, and people who have avoided linoleic acid for a long time.

Most of them have done a high-carb/low-fat (HCLF) diet the entire time, or at least for long stretches. Others have achieved a lot of depletion by significant amounts of fasting. Fasting is, of course, very low in total fat and absolute amounts of linoleic acid - zero! In a way, fasting is the ultimate low-fat diet.

My own experience also seems to show this:

As you can see I’ve taken an insane amount of OmegaQuant Complete (OQC) tests. Almost the entirety of that graph I was on a very-low linoleic acid diet in relative terms. But the diet was extremely high in total fat (~90%). And so even if my diet was relatively low LA, it wasn’t nearly as low as a low-fat diet can be.

The MASSIVE drop at 18 months is me on a rice diet, although that’s sort of a “temporary” drop only. But the very next number is my lowest LA result ever. It seems that a single month of eating near-zero fat has depleted my LA faster than 18 months of heavy cream.

Of course that’s only 1-2 data points. But it does seem to match the other anecdotes.

And this new (old, 1971 lol) pig study is another indicator: it proves that total dietary LA has a pretty big impact on adipose LA%.

By far the lowest LA% achieved was on either a 0% fat sugar diet, or a sugar + tallow diet.

I’d say it’s maybe a bit early to declare HCLF diets a total victory if one wants to deplete adipose linoleic acid.

But it seems likely, at this point. And if you’re leaning either way, I’d encourage you to give HCLPLF a try.

Remember: while I didn’t lose any fat eating a ~0% fat diet of exclusively rice & tomato sauce for an entire month, it was surprisingly tolerable.

At the very least, it’d be cool to see some other people do a before/after OmegaQuant Complete of a ~0% fat diet. That should help us figure out if this is just measurement noise or the huge finding it could be.

Next HCLFLP depletion diet?

I’m almost done with the Honey Diet (day 27/30 today). I was already pretty committed to doing another HCLFLP trial next. My thinking: it took me about 2.5 weeks to fully adapt to eating a high-carb diet both when I did ex_rice and for this honey diet.

Would be a shame to give up that (microbiome?) adaptation and start over again next time.

When I tried the potato diet years ago, I failed, probably because I couldn’t handle all that fiber - the diet just wasn’t sustainable for me.

As much as I love 30 day trials, some things just take a bit longer or don’t fully have a chance to spool up in 30 days. If that means chaining high-carb experiments instead of mixing them with 90% fat keto experiments, so be it.

I haven’t fully decided what I’ll do next, but here are some ideas:

• Grant Genereux’ low-vitamin A diet: white rice, beef, maybe some beans.

• Another go at the Potato Diet. Maybe I’ll do air fries + ketchup this time?

• The Real Kempner Diet: white rice + some fruit. No tomato sauce this time.

If you have any other ideas, or one of these sounds particularly interesting to you, let me know in the comments.

Note: OmegaQuant Complete on 20% sale until today (3/9/2025)

A reader let me know and I’m about to stock up on a couple more tests. It’s <$90 with the 20% discount. Check it out here.