Great stuff Natália, and most readable and well-written too!
Do you have any thoughts on the ‘seed oil’ idea? Which I’d express as:
unsaturated fats have gone from a tiny part of our diet to a huge part
the pathway that burns unsaturated fats is rate-limited for some reason, so over a certain low level, they clog up your metabolism and get saved for later
Therefore you can imagine that a person who has eaten a lot of seed oils/polyunsaturated fats can be overweight whilst still starving. And you might also expect them to have a slow metabolism and be showing the symptoms of mild hypothyroidism (low temperature, fatigue) without actually having a thyroid problem.
anti-seed-oil people would say that the problem is that:
the research is all wrong about what fats are saturated and what aren’t (because animals get fed on seed oils, so pork and chicken fat is largely polyunsaturated these days!)
and that even if you manage to cut out all unsaturated fats from your diet, you’ll still burn off the stored unsaturated fats very slowly.
At the moment this looks to me like a terrific idea that explains everything, but I’m trying to be sceptical and would really like to hear your thoughts against it.
and think it’s wrong, for roughly the same reasons as Scott, their excellent summary is: “If seed oils cause weight gain when people eat them, why didn’t seed oils cause weight gain when people ate them?” (in studies)
But the idea of a rate-limited path for digesting polyunsaturated fat just won’t get out of my head.… Our ancestors can’t have eaten much of it.
Hi Christian! I’m not sure I do believe it’s rate-limited, it’s more that if it were, that would be extremely interesting. I need a biochemist.
I’m imagining an enzyme going down a fatty acid, chopping carbons off one by one, and then it gets to a double bond and can’t cut it, so another enzyme is needed.
No question that we can digest mono-unsaturated fats, people have been eating olive oil in Southern Europe since forever, and I think that wild animals contain mono-unsaturated fats too, so that double-bond-cutter must exist.
But chopping the odd bond in something you’re not eating much of is different from chopping lots of bonds in something that’s a high proportion of your diet. (PUFAs have lots of double bonds, and make up something like 30% of modern calorie intake!!)
And yes, you could excrete the excess unsaturated fats, but our bodies aren’t profligate with energy, and fats are our storage mechanism, so I’m betting they get stored.
And indeed, a lot of human body fat these days is polyunsaturated. And a lot of the fat of food animals which are fed on seed oils.
Also, I’m told that cell walls are made from triglycerides made from fats, and that those fats should be saturated, and that these days they’ve got polyunsaturated fats in them. Change the structure and properties of cell walls and I bet all hell breaks loose. Some people have told me that cell wall structure isn’t affected by PUFA intake, and some people have told me that it is, and I don’t know....
As you may remember, I was once very interested in what looks like an epidemic of mysterious type-II hormone disorders..… So two of my idees fixes seem to be colliding here.
Storing fats actually needs the body to transport the fat into a cell. A basically unlimited transport into the cell while at the same time being rate limited to do something with them seems unlikely.
Hi Christian! I’m not sure I do believe it’s rate-limited, it’s more that if it were, that would be extremely interesting. I need a biochemist.
For this kind of problem, I would recommend starting with asking either ChatGPT or asking the question on a stack exchange website.
When making a hypothesis like that, where the phenomena should be well understood by experts, the best move is to put in work to check whether they are true instead of offering them as an open hypothesis the way you did above.
Great stuff Natália, and most readable and well-written too!
Do you have any thoughts on the ‘seed oil’ idea? Which I’d express as:
unsaturated fats have gone from a tiny part of our diet to a huge part
the pathway that burns unsaturated fats is rate-limited for some reason, so over a certain low level, they clog up your metabolism and get saved for later
Therefore you can imagine that a person who has eaten a lot of seed oils/polyunsaturated fats can be overweight whilst still starving. And you might also expect them to have a slow metabolism and be showing the symptoms of mild hypothyroidism (low temperature, fatigue) without actually having a thyroid problem.
This seems to me to explain an awful lot of stuff, but as Scott pointed out in https://slatestarcodex.com/2020/03/10/for-then-against-high-saturated-fat-diets/ all the direct evidence seems against it.
anti-seed-oil people would say that the problem is that:
the research is all wrong about what fats are saturated and what aren’t (because animals get fed on seed oils, so pork and chicken fat is largely polyunsaturated these days!)
and that even if you manage to cut out all unsaturated fats from your diet, you’ll still burn off the stored unsaturated fats very slowly.
At the moment this looks to me like a terrific idea that explains everything, but I’m trying to be sceptical and would really like to hear your thoughts against it.
The slime mold guys talk about this:
https://slimemoldtimemold.com/2021/08/18/a-chemical-hunger-interlude-e-bad-seeds/
and think it’s wrong, for roughly the same reasons as Scott, their excellent summary is: “If seed oils cause weight gain when people eat them, why didn’t seed oils cause weight gain when people ate them?” (in studies)
But the idea of a rate-limited path for digesting polyunsaturated fat just won’t get out of my head.… Our ancestors can’t have eaten much of it.
Why do you believe it’s rate limited?
Even if burning it would be rate limited, not everything that’s eaten gets metabolized. It can also be simply excreted.
Hi Christian! I’m not sure I do believe it’s rate-limited, it’s more that if it were, that would be extremely interesting. I need a biochemist.
I’m imagining an enzyme going down a fatty acid, chopping carbons off one by one, and then it gets to a double bond and can’t cut it, so another enzyme is needed.
No question that we can digest mono-unsaturated fats, people have been eating olive oil in Southern Europe since forever, and I think that wild animals contain mono-unsaturated fats too, so that double-bond-cutter must exist.
But chopping the odd bond in something you’re not eating much of is different from chopping lots of bonds in something that’s a high proportion of your diet. (PUFAs have lots of double bonds, and make up something like 30% of modern calorie intake!!)
And yes, you could excrete the excess unsaturated fats, but our bodies aren’t profligate with energy, and fats are our storage mechanism, so I’m betting they get stored.
And indeed, a lot of human body fat these days is polyunsaturated. And a lot of the fat of food animals which are fed on seed oils.
Also, I’m told that cell walls are made from triglycerides made from fats, and that those fats should be saturated, and that these days they’ve got polyunsaturated fats in them. Change the structure and properties of cell walls and I bet all hell breaks loose. Some people have told me that cell wall structure isn’t affected by PUFA intake, and some people have told me that it is, and I don’t know....
As you may remember, I was once very interested in what looks like an epidemic of mysterious type-II hormone disorders..… So two of my idees fixes seem to be colliding here.
Storing fats actually needs the body to transport the fat into a cell. A basically unlimited transport into the cell while at the same time being rate limited to do something with them seems unlikely.
For this kind of problem, I would recommend starting with asking either ChatGPT or asking the question on a stack exchange website.
When making a hypothesis like that, where the phenomena should be well understood by experts, the best move is to put in work to check whether they are true instead of offering them as an open hypothesis the way you did above.