My old theory, now refuted and renounced, was something like:
Double-bonds in fats are bad. They need to be broken in order to feed the Citric Acid Cycle.
Double bonds can be broken, but they need different pathway.
Human fat metabolism is designed to deal with animal fat.
Animal fat is half-saturated, half unsaturated, so it will have around 34 C-C bonds to one C=C bond, a ratio of 34:1
Polyunsaturated fat mainly means linoleic acid, which will have two C=C bonds to 17 C-C bonds, a ratio of 17:2
Too much PUFA, too many double bonds, overload that pathway. The relevant pathway has some slack, but it cannot deal with working four times as hard as it was designed for.
If you eat too much PUFA, some of your fuel cannot be burned.
That leads to:
Metabolic Slowdown, because your mitochondria are clogged with fats that cannot be burned
Fat level sensing corrupted, I don't know why. But one design for a total fat sensor is going to be something like: When I'm trying to burn fat, how much energy am I getting?
And that leads to:
Hypometabolism: You'll look mildly hypothyroid, including low body temperature.
And:
Your homeostat believes your fat stores too low
Your homeostat increases your appetite to try to add energy to your stores.
And that directly leads to weight gain.
That theory, which I have never formally believed, have sort of believed for the last six months, and now do not believe in, makes two predictions:
Action: Eat PUFAs over a certain safe level.
Result:
Too much PUFA to burn freely.
Your metabolism is clogged and runs slow
The spare fuel either hangs around in your cells, or gets stored as polyunsaturated body fat
Appetite increases
Weight gain
Tiredness
Stored PUFA levels rise
After a while, you don't even need to eat PUFAs any more. The stored PUFAs are enough to clog your metabolism on their own. Which means that even if you stop eating PUFAs, you'll still run slow.
And that's especially true if PUFAs are preferentially released from fat cells, which they may or may not be, I have no clue.
and:
Action: Stop eating PUFAs altogether
Result:
Only stored PUFAs fed into Citric Acid Cycle
Fat burns a little more easily
Metabolism runs a little better
Fat level signal becomes slightly more accurate
Homeostat realises fat stores are actually a bit too high
Loss of appetite
Weight Loss
You have slightly more energy
And also:
Stored PUFA levels fall
Everything just gets better in general, and the longer you keep it up, the lower your PUFA stores become, and the more you go back to normal.
And that's especially true if PUFAs are preferentially released from fat cells, which they may or may not be, I have no clue.
So now I want to try to tell the story of my life through the lens of the old theory.
In childhood I had little contact with PUFAs, never stored much, and everything just worked as it's supposed to do.
As an infant, I enjoyed cricket and played enthusiastically, but I hated soccer and mostly refused to participate, just standing around waiting for the soccer to be over, or even better hiding and reading a book, so I hardly got any exercise outside of cricket season.
I was in perfect health. Literally my only problem was hayfever (In my case an allergy to willow pollen, I think). And that's a traditional ailment. Just bad luck that my immune system one day confused a bit of willow pollen for an invader, and started fighting it.
My appetite was legendary. All my female relatives approved hugely. “Growing boys need their food”, they said, providing such in vast quantities. And I grew strong.
Not quite as strong as my grandfather, the steelworker, whom I once saw lift his wife and daughter off the ground, one on each arm. But I clearly took after him. I think if I'd ever had a manual job I might have have matched his extraordinary strength eventually. Needless to say I never did anything to deserve this strength. It just happened.
Grandad was always overweight. The fattest man I personally knew growing up. Looking at old photos of him now, it was nothing serious. A beer belly that you only see if he's not wearing a jacket. He ate as much as I did, maybe more.
My secondary school completely failed in its duty of providing sports for its charges, and we were largely left to our own devices on Wednesday afternoons. I remember a fair bit of ice-skating and ten-pin bowling, but that all stopped when I first discovered poker and Dungeons and Dragons. School threatened to throw me out if I carried on not-going-ice-skating-or-ten-pin-bowling, and I told them to swivel. They backed down.
School food was appalling. I refused to eat it. But I made enough money playing poker that I could usually get a chip butty and a can of Coca-Cola from the nearby fish and chip shop. These were great, and so I assume that they used butter on the bread and lard for frying. I never liked fish as a child.
I did do judo extramurally, a couple of hours once a week. I loved it and was pretty good. I was a member of an adult club, and there were full-grown men I could beat.
As an adolescent, I started smoking cigars in moderate numbers, and drinking alcohol in very large quantities, and I never really stopped. I spent a lot of time chasing girls and drinking and dancing and staying up very late. Walking miles to get home with my ears ringing from deafening music. At around fifteen years old.
I would occasionally buy chips fried in chip shops, and I assume that even in the mid-1980s they were abandoning beef dripping and lard for the cheaper and supposedly healthier 'vegetable oils'. Chip shop chips were always a bit disappointing.
But I always hated the taste of margarine, so that actually stopped me doing that too much, because what I really wanted were chip butties, and commercial chip butties were usually made with margarine, and it tasted horrible.
The ones at home and at my grandparents' were made with butter, and the chips were cooked in lard or beef dripping. Lovely. I ate tons of these, as well as anything else I could get my hands on. Lots of fried steaks, fried eggs (butter).
At around sixteen I left home and I briefly lived alone in town. I've no idea what I ate. Probably nothing sensible. I do remember a wonderful restaurant that sold fantastic burgers covered in melted cheese. They were huge and filling, so I probably didn't have chips with them usually. It was a long time ago and I don't remember. Lots of drugs though. Never heroin. I wasn't crazy.
I've got a few photos of me from around this time. I'm trim and healthy looking. I was five-foot-ten and I weighed ten-and-a-half stone. BMI 21. I took 32" waist trousers and my jackets were 42" regular fit. I scrounged a lot of my father's old clothes, which fit perfectly. Granddad's old clothes were far too big in all dimensions except height. I’m a bit taller than he was.
At university, I gave up drugs (bored) to concentrate on alcohol. I first encountered PUFAs in large quantities, in the form of chips fried in vegetable oil. They don't seem to have done much damage. I think my college canteen tried to provide a lot of different foods, and although I probably had chips with everything, they weren't, as it were, the main vegetable, and they weren't as good as the ones at home anyway.
At university, I didn't do a great deal of sport, although I did tend to get roped into college sports teams when they were short a man.
For most of my life after university, I was very sporty.
As I came into my full adult strength, I got much broader and heavier. At twenty five I was thirteen and a half stone, still 5'10". BMI 27. Technically overweight but no one would have called me overweight. I chased girls and they chased me. I took up rugby and rowing. I was quite bad at both, but it was lack of skill. Physically I was born for rugby. Rowing I'm not tall enough, but I was strong and fit.
I think at this point I was probably carrying a bit of spare fat round the gut. Nothing to write home about, but I remember noticing and not caring.
I took 44" regular jackets and 34" trousers. Some of the clothes I bought then have lasted me my whole life. I still have them.
My father's clothes no longer fit me. They were very tight round the shoulders. Granddad's jackets were perfect, but his trousers were far too large round the waist and too short. One particularly nice suit I had taken in.

For most of my life after university, because I never married (I'm not crazy), I lived alone.
I usually ate out for lunch most days, because it's easier and more sociable than cooking a proper meal at home. In England if you eat out it comes with chips.
My workmates thought I was strange, because I'd always go to the pub for lunch but never drink alcohol. Always coffee. I usually drank in the evening, but during the day I wanted my mind clear.
In England in the 1990s, beer for lunch was not quite mandatory, but certainly expected.
This almost certainly involved eating quite a lot of PUFA-fried chips. I'd grown used to the funny taste and didn't mind, although I still hated margarine and wouldn't eat anywhere that used it.
I noticed that I was often slightly tired after lunch.
I remember I put that down to both the effect of my lunchtime smoke, usually the first of the day, and the carbohydrate load making me sleepy post meals. I don't ever remember noticing that after eating carbs at home though.
I mainly lived, as most fanatical sportsmen do, on vast quantities of carbohydrates. At home I would think nothing of making a saucepan full of spaghetti, the biggest that would fit on the stove, adding some tomato sauce and butter, and eating it all.
Another favourite was white bread and cheshire cheese sandwiches, microwaved briefly to melt the cheese. Anything easy, really! Repeat until not hungry any more.
I did notice that my aerobic performance, while very good throughout this period, was not quite as good as that of my friends, given that we were doing the same insane amounts of training. Although I was way fitter than most people, I was always distinctly second-rate by fanatical sporting standards.
If you have any sense, you'll be asking at this point why I didn't stop drinking and smoking if I was so sporty. The answer is that I was doing it for fun. If you have to make sacrifices to get a tiny bit better, that's not fun. You're missing the point. Half of sport is going drinking afterwards.
Boat clubs had ashtrays on the tables in the bar, in my day.
To my shame I confess that I sometimes gave up smoking for a month before important boat races, to sneak an advantage from liberating my red blood cells from their loads of carbon monoxide. But I always celebrated afterwards with fags and booze. Win or lose, as they used to say.
I noticed that I seemed to be aging faster than other people.
By the time I hit forty I was starting to feel that my rowing days were over. My aerobic performance was better than it had ever been, but on the back of more and more training every year. I began to feel that competing in a pure-fitness sport against twenty-five year olds was getting silly, and I'd got as good as I was ever going to get. I wasn’t really enjoying it as much as I had used to. It had started to hurt my legs. So I stopped.
The best friends of my life, men I would have died for, and who would have died for me, carried on without me. Some of them were older than me.
I started quickly losing muscle mass and gaining fat, I think, although I wasn't measuring anything at this point so I don't know.
In hindsight this is odd. It's obvious why without the intensive rowing I was losing muscle, but why was I gaining fat?
This was the point where I first started to think about diet, and it occurred to me that large quantities of carbohydrate from grass seeds probably wasn't what we were designed to live on. ( The glycaemic index/glycaemic load theory, or early paleo. I didn't know enough about evolution in those days to realise that most of my relevant ancestors were farmers.)
I stopped eating the vast quantities of pasta and bread that I was used to eating, but I never gave up chips. I liked them too much, and I thought that being impregnated with fat would slow down the absorption of the carbohydrates. At first I was mainly making chips at home in my own deep fat fryer, using beef dripping.
I also tried Seth Robert's 'Shangri La Diet', eating a tablespoon of Extra Light Olive Oil every morning and trying to avoid tasting it, which really did seem to work as advertised.
My appetite collapsed, and I started losing weight instead of gaining it. I didn't track my weight explicitly, but I had to tighten my belt a couple of notches. Problem solved, I thought.
Rowing was the only thing I'd stopped doing at this point.
But I noticed that my cycling performance was dropping off too. I'd always been easily able to keep up with my friends while cycling, and although I wasn't the fittest of the bunch, I would occasionally take a turn at the front, but suddenly I started dropping off the back, and quite soon I was unable to keep up even by draughting. That spoiled cycling for me, and so I stopped doing that too, and sold my racer.
But I was OK generally. Just no longer a fanatical power-endurance sportsman. I satisfied my sporting urges with a new love of cricket, which had never seemed much like exercise to me before, too much standing around.
I think at this point my trousers were still 34", which is what they had been my whole adult life. I actually think that I wore slightly larger jeans than necessary usually, because my thighs were large compared to my waist. I always needed a belt to hold them up.
Then I bought my narrowboat and moved on to it. Electricity supplies were limited.
I didn't want to use a standard chip pan because I knew I'd cause a fire by making chips while drunk, and my electric deep fat fryer was impossible on a boat.
But I kept eating chips, just more and more I was buying them from commercial sources.
I think this resulted in PUFA overload, and I got more and more tired. My general state became lethargic, I started sleeping more and more, and waking up unrefreshed even after sleeping for thirteen hours or more.
My once-heroic alcohol tolerance collapsed. I'd get terrible long hangovers from quite small amounts of drinking.
I realised that I was actually ill when, in the middle of an interesting mathematical programming project for a client, I just lost the ability and even the desire to read my own computer code. Programs that I was in the middle of writing suddenly seemed incomprehensible. I couldn't work out what they were supposed to do. As if they'd been written by a cleverer man. It was scary.
Over the next few years I got more and more tired. I did manage to hang on to Saturday cricket by sheer force of will, although it was exhausting and not much fun any more.

I ended up taking thyroid drugs to fight off the tiredness.
This worked really well, my life came back, I could program again, and I almost forgot I was ill apart from the daily drugs.
I even found I could drink moderately again, although never again in the carefree way I used to. I drank less and less as time went on though. It was just less and less fun.
More like a poison I could tolerate than a stimulant I enjoyed.
But some of the old vivacity seemed to have gone. An old friend from rowing recently described me as seeming like: "A man with limits who'd accepted those limits and learned to live within them".
He mentioned this recently in the context of me seeming somewhat restored. He said it was "Like having the old John back".
“Whatever you’re doing”, he said, “Keep doing it”.
I even took up tennis, a new sport and more exercise than cricket, and I was fairly fanatical about it as usual.
I noticed that exercise made me tired now, instead of energizing me as it used to do.
After a session of tennis I usually needed to have a bit of a rest, both mentally and physically.
Cricket was the same. What had once seemed a light-hearted run around in the sunshine mainly as an excuse for a beer was now an exhausting day that needed prepared for, and needed recovering from.
I think the Chronic Fatigue Syndrome people call this 'Post-exertional Malaise', and it's a principal symptom of the syndrome. Mine was very mild compared to the many CFS horror stories that I've read and heard about.
But mostly my health problems were sports injuries. What was 'admirable flexibility' in a thirty year old became 'mild joint hypermobility' in an old man of fifty. I was always pulling things and straining things. That caused me to reduce the amount of tennis I played. It's a hard game on the joints.
This was all quite stable until the pandemic. I played tennis three times a week for half the year, and cricket two or three times a week in the summer months.
At some point I did start wearing 36" trousers instead of my customary 34"s. Don't remember when. Didn't seem like a big deal. Middle aged is middle aged.
I wasn't going to try the Shangri-La Diet again, it had happened far too close to the point where the awful tiredness had started, and maybe my clever metabolic hack had damaged my metabolism. I didn't think so, but no way I was taking that risk. I'm not crazy.
At the first hint of the new coronavirus, I formed a 'bubble' with a friend of mine. We cut contact with other people, laid in supplies and made plans to flee town if necessary, and I stopped drinking entirely. The situation was scary and I wanted my wits about me.
I remember having enormous energy at the start, desperately working out what was likely to happen, what needed to be done to survive, how to save my family and vulnerable friends from the horror that was boiling out of China, obsessing about how viruses worked, how they spread, how to kill them. What the consequences would be, how to survive the possible civil unrest if everyone was ill at the same time and the background processes that support our daily life in paradise stopped functioning.
All eating out stopped in the pandemic. You could buy take-aways, and we did occasionally, but mainly we were eating home-made food of very high quality. Kate cares about nutrition in a way I never had. She won't eat anything with 'too many ingredients'.
I loved the lockdowns. The great planet-poisoning shit-machine shut down for a few months. The weather was good, we took Kate's dog for walks in the sunshine, dinner together and watching Black Mirror together every night. The closest thing I've ever been to married, and it suited me much better than I ever thought it would.
I remember endless energy and an optimistic sunny mood throughout.
I took up online chess. I'd always known how to play but this was the first time I'd ever put serious effort into getting better. My rating rose from 800 to 1200 fairly smoothly over a few months. Then I decided that I'd spent enough time playing what was essentially a video game, and stopped playing regularly. But it was a great way to keep myself entertained while there was not much else to do.
Kate worries excessively about her weight. Always has. Is always starving herself to try and stay normal. I tried to convince her that if you left your weight to its own devices, ate when you were hungry, and didn't eat when you weren't, your weight would just settle down at whatever its natural level was. You might be a bit heavier than you'd like, but you'd be at peace.
As part of this, I took my weight measurement for the first time in a long time. 93kg at the start of the pandemic. I was surprised that it was so high. I vaguely remembered 85kg/thirteen-and-a-half-stone as being 'my weight', like 5’10” is ‘my height’, but I just figured that middle-age-spread is a thing.
We took weight measurements occasionally. Mine was always 93kg.
A year later, when everything had started getting back to normal, 93kg.
Like I said, if you just eat what you like, when you like, your body finds its level and stays there. Kate did not, and does not, believe me. She gave it a try, ballooned, and panicked.
[ Kate comments: My thinking is a bit misrepresented! - after "ballooned and panicked" you might say that Kate believes her appetite signals are haywire from years as a full time athlete eating c.5000kcal a day!
Also the ballooning - a clear and direct result from consuming my bodyweight in alcohol plus 5000kcal a day while Sammy [the dog] disastrously poorly and I was the most miserable of my life! :-) ]
After things got a bit more normal, we stopped being a bubble, and I went back to my old ways of mostly eating out, with occasional snacks at home.
I didn't really eat much except my lunch out, not doing vast amounts of exercise any more (Cricket had stopped and my team never re-started. Tennis restarted but I never played fanatically again. I kept buggering joints.)
I never did take up alcohol again. Every time I tried a beer or a glass of wine it made me feel ill, and the hangovers were long and nasty. So I became a teetotaller.
I'm a middle-aged Englishman. We don't really do teetotal. Alcohol is our social lubricant, our 'Pastime with Good Company', as good king Henry sang. I lost a lot of good friends just because our common interest in getting drunk no longer worked for me, but I adjusted, and got used to my new lonelier post-pandemic life. I found some new interests that didn't revolve around alcohol or sport.
It all went wrong again, around the time of my second coronavirus vaccine. It gave me fatigue, a normal and expected side effect, but the tiredness from that never went away.
You can actually see the effect in my chess rating:
https://www.chess.com/stats/live/rapid/johnlawrenceaspden/0
In April 2021 I started playing regularly online again, and my rating rose smoothly from 1200 to 1300. And then suddenly in June I seemed to go blind. I lost games because I missed things that should have been obvious. My rating dropped sharply from 1300 back down to 1200.
A friend said that he'd had the same effect for a couple of weeks after the vaccine, but with me it never went away. I was so disheartened that I stopped playing chess altogether. It was dispiriting to always be making stupid errors.
After that I was ill again. Very mild 'chronic fatigue syndrome', but still limiting and disabling.
I tried upping my thyroid dose, but it didn't work. It just made me hot and anxious on top of the tiredness. So I put the dose back down again.
At one point as an experiment, I tried dropping my thyroid dose a bit. That was nearly a catastrophe. I don't think I got out of my dressing gown for a week.
All alone in the wilderness I went into a period of lethargy so deep that I'm surprised that I reacted correctly and put the dose back up.
A couple of days later I came back to myself, and found that all my pot plants were dead. I remembered noticing that they needed watering, and making a mental note to get round to it when I had more energy.
I threw the decorative ones away, and ripped up the edible ones for dried herbs and mint sauce.
By Christmas 2022, it was obvious that this new bout of post-vaccine tiredness wasn't going to go away.
I didn't feel like working, had again lost my lifelong interest in tinkering with computer programs. I was still playing tennis regularly, although it was exhausting. I'd never taken up cricket again. Then I got a knee injury that wouldn't heal, and I gave up tennis. My last sport, gone.
I needed new trousers. 38" this time.
I re-measured my weight. 97kg on the same scales. Up 4kg in a year. For the first time in my life, I started to worry about my weight. 4kg/year doesn't end well.
I got interested in the causes of the obesity epidemic.
Of all the possible explanations out there, the one about polyunsaturated fats, which I'd first read about by hazard in Scott Alexander's article back before the pandemic in 2020, seemed the only plausible one.
And it occurred to me that it might explain all the other 'diseases of modernity' too.
So just before Christmas 2022, I first Renounced All Polyunsaturated Evil. To see what would happen.
This blog has been the story of that year, 2023, in which I have avoided all polyunsaturated fat.
I felt much better immediately. My appetite and energy went way up.
I came back to life a bit.
Now all the other noise from processed food was gone, I noticed that I was intolerant to sulphites.
Giving up sulphites resulted in a huge further improvement in my well being, and I could drink again!
Turns out I can still drink like an adolescent, as long as it's spirits. Anything with sulphites in it is the problem. Alcohol is still just fuel. I'm not sure I want to go back to my old ways, but I can if I like. I restrict myself to the odd vodka or whisky in the pub mainly.
But my weight carried on rising rapidly.
At some point in April, I found myself having to buy yet more new trousers. 40" waist this time. Although I thought: "well, you're a growing lad again", and bought 42"s instead. To allow room to grow.
I weighed myself again. 99kg. 2kg in six months. 4kg/year, just like before.
I figured no-PUFAs, no-sulphites was helping the tiredness, but now I had to do something about my skyrocketing weight.
So I bought a set of scales, calibrated them against Kate's scales, and started taking daily weight measurements, and keeping notes about my mood, weight, energy levels, waking temperature and thyroid dose.
And then I started looking explicitly for ways to lose weight.
And I found u/exfatloss and his substack: https://exfatloss.substack.com
The last six months of various ex150-like things I have done, I have written about rather extensively in previous posts.
But I want to notice that my old theory, which I no longer believe, and have renounced, does quite a good job of explaining my whole life.
PUFAs (or at the very least, chips fried in rapeseed oil) could well, as my consumption of them slowly rose for various reasons, have slowly crippled my formerly excellent metabolism as I grew older.
Could well have crippled it to the point where I needed to overdrive that metabolism in order to function. Aging fast.
Could well have eventually crippled it to the point where I couldn't overdrive it any harder, and even with the thyroid, I started to fail again.
Giving up PUFAs seems to be associated with things getting better.
That old theory kind of works, as an explanation.
But there are a few little details about this last year, where I was keeping careful notes, which it does not explain.
So I need a new theory, but maybe it does not need to be too different from this old theory.
Just an epicycle here and there, maybe.
Great read. Why is it that middle-aged Englismen can essentially write about anything and it turns out fascinating and you wish you were there?! I truly believe this was the foundation of the British empire. (Is the E in empire capitalized?)
PUFA theory sure lets us draw quite a good line through all the points in our history. But, of course, it's easy enough to find an infinite number of lines to fit. The true test will be if It All Goes Away after X years of dePUFAcation. Hopefully we'll find some sort of useful proxy, like OmegaQuant or whatever, so we don't have to tell people "just keep going down this path for 7 years, trust me."
And in the meantime, it sure seems that PUFA acts as a sort of background radiation/catalyst for all sorts of more specific problems and puzzles that can be solved in the short-term: keto seems to circumvent certain ailments, protein restriction others.
Would these just work on their own, in absence of PUFA? Maybe. What makes me suspect this is that not everybody who's clearly metabolically messed up needs to restrict protein, or carbs. But of course that could also just mean it's genetic.