Fire in a Bottle is a blog arguing that polyunsaturated fats and related metabolic mechanisms drive obesity, with diet proposals like the Croissant Diet.
HN commenters recommend it in nutrition threads, especially on seed oils and saturated fats, though one admits not following the science.
> The same UC Riverside research team found in 2015 that soybean oil induces obesity, diabetes, insulin resistance, and fatty liver in mice. Then in a 2017 study, the same group learned that if soybean oil is engineered to be low in linoleic acid, it induces less obesity and insulin resistance.
> “The hypothalamus regulates body weight via your metabolism, maintains body temperature, is critical for reproduction and physical growth as well as your response to stress,”
Italics mine.
Linoleic acid is what induces torpor (hibernation) in mammals. We are mammals. People in the modern world are possibly something like half hibernating, inclusive of mental effects and of course the effect on difficult-to-remove-weight. The rise in Soybean oil consumption is an enormous change in the human diet over the last 50 years. The scale of it replacing so many fats, especially formerly animal fats, is just huge.
See: Humans and Hibernating Mammals React to The Same Amount of Dietary Linoleic Acid in the Same Way. By Becoming Torpid.
https://fireinabottle.net/humans-and-hibernating-mammals-react-to-the-same-amount-of-dietary-linoleic-acid-in-the-same-way-by-becoming-torpid/
(I submitted that article because I think its worth its own discussion: https://news.ycombinator.com/item?id=30456454)
The million dollar question!
No one really knows. There are some theories.
One thing is linoleic acid converts into endocannabinoids, which stimulate appetite. Too much n6, too much appetite, obesity, is the theory.
If you google around on e.g. pubmeb you can find various papers proposing this.
But there's probably more to it than that; there are pig and mouse studies where the animals are fed isocaloric diets, but the animals eating high LA get fat. So that strongly suggests that it's not just a appetite-based overeating thing.
The blog hyperlipid proposed a theory involving ROS signaling at a cellular level; my knowledge of biology and metabolism is sadly minimal, but at a very high level I think the theory is something like, "having too much linoleic acid in the diet signals cells to remain unnaturally insulin-sensitive and accumulate fat".
See also: the blog Fire in a Bottle, which tries to summarize the hyperlipid theory at a less low-level, technical level.
https://pubmed.ncbi.nlm.nih.gov/27350414/
https://high-fat-nutrition.blogspot.com/2013/08/protons-so-far-some-sort-of-summary.html
https://fireinabottle.net/the-ros-theory-of-obesity/
Is there anything to the idea that saturated fats are less prone to blocking glucose metabolism? For example, this guy [1] argues that saturated fats can temporarily suppress insulin signaling to avoid overloading the cell with glucose while the fat is being metabolized.
Anecdotally I have a much easier time handling carb-rich meals since mostly eliminating polyunsaturated fats from my diet. My previous experience was some combination of “food coma” and “noticeably hangry” a few hours later, but now I mostly just feel energetic for a few hours.
Some of the most metabolically-healthy populations in the world eat mostly starches [2] (and maybe 1–2% of calories from PUFAs), so my hunch is that eating low-carb is more of a workaround for widespread metabolic dysfunction than a requirement to be metabolically healthy.
[1] https://fireinabottle.net/the-ros-theory-of-obesity/
[2] https://fireinabottle.net/pontzers-burn-and-metabolic-rate-mechanisms/
(It’s worth pointing out that both of these links are from a site that also sells supplements, but they do link back to the primary sources)
I currently mostly use coconut oil or butter for cooking and olive oil for taste (salads, hummus).
I don't understand any of the science that I've tried to read (and watch). How misc fats like PUFAs metabolize and so forth.
The Fire In a Bottle guy has explainer videos. Alas, I'm in no way competent enough to judge how good that info is. It seems to jive with other advice, eg Dr Terry Wahls and Dr Rhonda Patrick and Dr Peter Attia. But what do I know? https://fireinabottle.net https://www.youtube.com/watch?v=Jjt6C_7Vgw4&list=PLo4Cmo9MNYmm_MCLowkfJRCL4KxMlGyss
Nor am I able to assess tradeoffs. Like with the nootropics stuff, I worry about over optimizing (or just plain wasted effort), where the rewards don't merit the effort.
My impression is the metabolism science is progressing quickly. Esp wrt cholesterol. (I have a stubbornly high LDL, hence my interest.) I'm optimistic that sooner than later some consensus will emerge and some one can just tell me the correct answer and I can get back to coding.
Also there seems to be some evidence that the imbalance of Poly-unsaturated Fatty Acids and Saturated Fatty acids in our foods combined with high carbohydrate intake that may be contributing to overeating by turning our body fat into a sort of parasite that preferentially consumes calories to make more fat rather than allowing our organs first pick.
https://fireinabottle.net/the-scd1-theory-of-obesity-part-1-insulin-leptin-scd1-and-thermogenesis/
I am aware this site is trying to sell you something but the 3 part dive into research literature makes me feel like they might be onto something with this.
Brad Marshall[0] makes a case for the benefits of stearic acid (C18:0), which is predominant in beef tallow and cocoa butter. It acts as a beneficial metabolic signal that promotes mitochondrial fat oxidation, higher energy expenditure, and leanness—counteracting the obesogenic effects of polyunsaturated fats (PUFAs), especially linoleic acid.
[0] https://fireinabottle.net/every-fire-in-a-bottle-post-from-the-beginning/
EDIT: I'm sympathetic to Brad's argument and I'm concerned that RFK Jr's incompetence will interfere with ongoing research in this area of metabolism.