I say nutrition is tied to fitness so Imma drop this here.
Inflammation what about it!?!? What is it and how do we get it. Well a big one is Omega 6 fat. Here's a little breakdown of some thoughts I have on what's happening internally and what/why I use the ones I use.
I cook mainly in tallow and butter.
https://stasher.news/uploads/1048
That's linoleic acid, the main omega 6 fat, grams per 100 g of cooking fat, straight from USDA FoodData Central. Look at the bottom. Butter 2.2, beef tallow 3.1, coconut 1.7. Look at the top. Safflower 74.6, grapeseed 69.6. That gap is the whole story.
Why omega 6 inflames your cells
Your body builds cell membranes out of the fat you eat. Saturated fat is a straight chain, no double bonds, so it packs in tight and stable. Polyunsaturated fat has kinks, and those double bonds are also oxidation targets. When linoleic acid sits in your membrane and oxidizes, you get oxidized linoleic metabolites, and those show up concentrated in atherosclerotic plaques (that's the gunk that builds up in artery walls, the stuff they talk about in every heart attack story). Your body also converts excess LA into arachidonic acid, which feeds prostaglandins and leukotrienes (the signalling molecules your cells use to actually run inflammation). More substrate in, more inflammatory signalling out.
The omega 6 and omega 3 thing
Omega 6 fats are not poison. They're essential, your body can't make them. Omega 3 fats are essential too and they actually work together, omega 3s lean anti inflammatory and omega 6s lean pro inflammatory, and the ratio between them is what your machinery reads. For most of human history that ratio sat around 4 to 1. Today it runs 15 to 25 to 1. Same fats that were fine in balance are drowning the omega 3 side out, and it's the same deal as cholesterol. Cholesterol got a shitty name but it's essential, it's the raw material for every cell membrane and it's what your skin turns into prohormone D, vitamin D, when the sun hits it. Essential nutrient with a bad reputation because the dose and the company it keeps went sideways.
How much more we eat now
Around 1909, linoleic acid was about 2.8% of American calories. By 1999 it was over 7%, today estimates run 8 to 10%. Soybean oil per person went up more than 1000 fold in that century. Nobody chugged that oil. It went into the food supply.
It hides in the meat too
This is the part that sucks. Pigs and chickens are monogastrics like us. They build their body fat out of their feed, and chickens are out there pecking away at corn and soy all day, so they're loaded. That's why chicken fat sits at 19.5 on the chart while beef tallow sits at 3.1. You can eat clean, no fried food, no bottled seed oil, and still load up on omega 6 through chicken thighs and bacon. Cattle are built different, the rumen hydrogenates the feed fats before they ever reach the body, so the cow actually soaks a lot of that omega 6 out and stabilizes it. Beef stays low even grain finished. It sucks, but it's still way less. Grass fed is better again on top of that.
The heart attack flip
Here's the interesting part. When they talk about heart attacks they talk about saturated fat and cholesterol. But cholesterol doesn't just wreck an artery by sitting there. It gets damaged by oxidation, and the oxidized linoleic acid metabolites are the things concentrated in the plaques themselves. So the story might actually run the other way: it's not the butter, it's the sea of omega 6 the butter got replaced with that oxidizes, plaques up, and gets blamed on the fat that never left. It's the type of fat, not the fear of fat. Siloed into one villain when the real answer is way simpler.
The pan matters too
Polyunsaturated fat oxidizes outside the body as well. Heat plus oxygen plus double bonds. Saturated fat has no double bonds so there's nothing to attack, that's the whole reason I love it. That's why tallow and butter survive a hot pan while seed oils go rancid. The high smoke point on refined seed oils is marketing, the oxidation starts well below the smoke point.
Every cell you've got is built from whatever fat you ate last month. Feed them straight chains and they run clean. That's the whole project, really. Keep the engine the cells are running on stable and everything else gets easier.