This is Your Body Temperature on Vegetable Oil


This article suggests that the reason the Tsimane people of Bolivia experienced a significant, well-documented drop in their body temperature and metabolic rate over the past 15 years is that their fat became less saturated due to newly available “store bought foods”, most of which are loaded with polyunsaturated fat (PUFA).  This drop in body temperatures mirrors what has happened globally as vegetable oil consumption has increased worldwide.

If you’ve been following along with The ROS Theory of Obesity and The SCD1 Theory of obesity Part 1 and especially Part 2, you will know my theory that increasing the saturation level of fat entering the mitochondria – both from stored body fat and from diet – increases your metabolic rate.  This happens because saturated fat causes Reactive Oxygen Species (ROS) to be produced in the mitochondria.  ROS is a signal to the nucleus that the body is burning fat and that energy levels are high.  The ROS lead to an increase in thermogenesis, which means literally “making heat”.  Thermogenesis literally burns off calories as heat.

I am speculating, of course.  I don’t know the types or quantities of store bought foods that are being consumed by them.  The potential mechanism by which vegetable oil could reduce metabolic rate is well known, however.

Human Body Temperatures are Dropping!

Several interesting papers came out in 2020 around the issue of declining body temperature. The first pointed out that the body temperature of Americans has been decreasing since the industrial revolution.​1​

An even more interesting one showed a decline of body temperatures by 0.5 degree C (0.9 degree F) in an Amazonian population that was well documented and happened between 2004 and now.​2​ Here is a graph from that paper of the average body temperatures of men and women at different ages with samples taken between 2002-2004, 2007-2012 and 2013-2018. I think the Female temperatures are particularly compelling.

From 2002-2006, female body temperatures were right at 37.0 for the entire human lifespan. By the 2007-2012 time period, young women had a small drop in average body temperature and older women had a significant drop. By 2013-2018 the body temperature of women of all ages had collapsed to a new average of 36.6 degrees. This is an interesting number, because the first paper states “Recently, an analysis of more than 35,000 British patients with almost 250,000 temperature measurements, found mean oral temperature to be 36.6°C”. So the Bolivian “Forager-farmers” now have the same body temperature as modern Britons.

The drop in temperature was accompanied by a drop in metabolic rate. Unfortunately, metabolic rates did not begin being measured until 2012, when they were in steep decline before plateauing in 2014.

The hypothesis of both of these papers is that infections cause increased body temperatures – as you know if you’ve ever had the flu – and the reason that body temperatures have declined over time is that humans have eliminated many sources of infections including parasites. Ultimately, though, the Bolivian paper concludes, “Despite the possibility that changing infection rates and reduced morbidity can explain some of the temporal decline in body temperature, several lines of evidence suggest that these changes alone are insufficient. … These observations suggest that factors other than inflammation and immune activation are likely to influence body temperature.”

The paper, however, gives little indication as to the diet of the Bolivians or how it might have changed. But this pop-science article about the paper gives a little insight, “The Tsimane people live in villages without running water or electricity, and subsist largely on rice, plantains and the starchy root vegetable manioc. Rapid community changes over the last few decades include increased access to store-bought foods and antibiotics.”

So the Tsimane had a very high starch diet to which, during the time period that their body temperatures were dropping, they added “store-bought foods”. As you probably know, store bought foods are a fantastic source of vegetable oil. I would suspect that vegetable oil itself would be in demand for adding to starches.

Does Vegetable Oil Lower Body Temperature?

Luckily, this paper also came out in 2020.​3​ This is a mouse study. Look at how much the body temperature of mice whose diets are supplemented with margarine plunge when subjected to three hours of cold compared to their starch eating counterparts. Sorry about my arrow drawing skills.

 The same paper showed that mice fed margarine had a buildup of linoleic acid (PUFA) in their tissues.  Compared to mice fed butter, they had lower body temperatures and produced less UCP1 (more on that below) in the fat cells.  They failed to do thermogenesis in response to cold!

Mice fed butter (the left image) have a higher body temperature than mice fed margarine (the right image) after a three hour cold exposure. Note much higher percentage of red and yellow (warmest areas), green (next warmest) and less blue and purple (coldest) in the butter fed mice.
The butter fed mice make lots more UCP1. The paper is ostensibly about Omega 3 supplementation. That’s not a rabbit hole I want to go down here. I’m just using the butter Vs. Margarine comparison.

Introducing UCP1

UCP1 is an “uncoupling protein” that is increased in the mitochondria of metabolically active brown and beige fat cells in response to Reactive Oxygen Species (ROS) production.  

As I’ve said before, the mitochondria is like a battery.  When fuel (fat or carbohydrate) is being burned, the Electron Transport chain pumps protons across the inner membrane, causing a voltage gradient.  The outside of the membrane has a positive charge and the inside has a negative charge.  It’s exactly like the positive and negative terminals of a battery.

The mitochondria uses this voltage gradient to do work.  Typically, as the protons flow back through the membrane, through Complex 5 of the electron transport chain, the energy released is used to turn ADP into ATP.  What the body is doing in all of this is converting one type of stored chemical energy (the hydrocarbon bonds in fat) into another type of stored chemical energy (ATP), that can then be used to do work – move a muscle.

UCP1 is an alternate route for protons to flow back through the mitochondrial membrane.  Normally, a battery would be used to do work, just like in the mitochondria.  For instance, a battery can turn on a light bulb.  The light bulb is doing work – providing light.  The light bulb provides “resistance” to electrical flow to do this work.  Because of the “resistance” the electrons move slowly from one terminal to the other and a flashlight can turn on a bulb for quite some time.

What happens, though, if you just connect one terminal of the battery to the other without any resistance?  The electrons can flow through RAPIDLY and give off a tremendous amount of heat.  Very quickly, the voltage difference between the positive and negative terminals of the battery can be dropped this way.  Soon, the battery will be discharged and no longer capable of performing work and a large amount of heat will be given off. Some people do this for fun:

So each UCP1 protein that  is produced is like a tiny filament short circuiting the mitochondrial “battery”.  It allows protons to flow back through, releasing energy from fat as pure heat, rather than storing it in another chemical form.  When this happens, one magically burns off excess calories, body temperature rises and the voltage gradient across the mitochondrial membrane drops.

The margarine fed mice fail to produce UCP1 and fail to do thermogenesis.

What About The Starch Eating Humans?

I’m a huge fan of the study known colloquially as “The China Health Study”​4​, despite disagreeing with the conclusions of the authors about almost everything.  The raw data they’ve collected is great and the original manuscript is fun to flip through to get ideas.  You can pick up a copy at Amazon for only 500 bucks.  One conclusion of the authors I DO agree with is this (emphasis mine), “ In the China Study, the least active Chinese consumed 30% more calories than their American counterparts yet their body weight was 20% lower. The excess calories were lost as heat rather than being stored as fat.”

So starch eating Chinese are very good at doing thermogenesis.

If highly saturated fat entering the mitochondria is what allows for thermogenesis, why then do the starch eating mice and starch eating humans have high metabolic rates and body temperatures?

The answer comes down to body fat saturation levels.  The truth is that the body fat of starch eating creatures is highly saturated.  I’ve seen this first hand in pigs and this is the whole basis of my Firebrand Meats Low-PUFA pork.  

In the SCD1 Theory of obesity part 2 I highlighted a Tweet from Nathan Owens where he posted his results of a blood test showing the fat composition of his red blood cell membranes.  The “China Health Study” reports the fatty acid composition of red blood cell phosphatidylcholine, which is to say membrane fats.  That is also what is being reported in the test from Nate.  Nate is a lean American, who eats a keto/mostly carnivore diet.  Look at how unsaturated the body fat of a lean American eating lots of beef is compared to that of a Chinese person eating mostly starch!

NathanChinese MeanAmerican RangeChinese Range
Omega 6 PUFA30%27%26-45%20-36%
Omega 3 PUFA9.7%3.3%0.7-11.5%

As you can see, there is ZERO overlap between the saturated fat levels of Americans and Chinese.  All of the Chinese sampled had MUCH more saturated fat than Nate did and Nate is at the very high end of the American range.  According to the company, the Americans with the most saturated fat have way less than the Chinese with the least.

Why is this?  The body fat of people who eat mostly starch comes from DNL (De Novo Lipogenesis), which is only able to produce saturated fat, some of which gets converted to monounsaturated fat via the action of SCD1, which starch eating people don’t make too much of.  Starch consumption from birth, if your mother and grandmother were also starch consumers, gives you very saturated fat!  Saturated fat gives you ROS.  ROS gives you the ability to produce UCP1 in your beige fat cells and burn off extra calories via thermogenesis.


It is well documented that the average body temperature and metabolic rate of the Tsimane people dropped over the last 15 years as they added “store bought food” to a diet of rice, plantain and manioc.  Proposed reasons for this drop are reduced levels of infections, which is not supported by the evidence.  I am proposing that polyunsaturated fat from the store bought foods were the key factor leading to the drop in body temperature.  

I propose that the levels of PUFA from the store bought foods built up over the years in their fat cells,  resulting in a steady decline in mitochondrially produced ROS,  leading to a drop of production of uncoupling proteins and a reduction in thermogenesis.

Technical Details!

 In the fat comparison between American’s and Chinese I’m using red blood cell membrane composition as a stand in for stored fats.  The composition will be different – membranes need to be very fluid and so they are very high in unsaturated fats and PUFA.  Stored fats are much more saturated.  But blood cell fats are easy to test and stored fat requires a biopsy.  My opinion is that they will be tightly correlated: those with highly saturated membrane fats will have highly saturated storage fats.

I’ve had some questions about what is actually being tested in this test – membrane fats or whole blood.  I talked to the company this morning and they told me that they separate out the phospholipids (membrane fats) from the other fats (stored for energy purposes) from the blood samples. They also said that the test will represent ALL phospholipids in whole blood – red blood cell membranes as well as the outer layer of LDL cholesterol particles (for instance).  Finally they said that red blood cell membranes are the easy majority of the phospholipids, so that in their opinion the test is pretty accurate as to the composition of red blood cell membranes.  

  1. 1.
    Protsiv M, Ley C, Lankester J, Hastie T, Parsonnet J. Decreasing human body temperature in the United States since the Industrial Revolution. eLife. Published online January 7, 2020. doi:10.7554/elife.49555
  2. 2.
    Gurven M, Kraft TS, Alami S, et al. Rapidly declining body temperature in a tropical human population. Sci Adv. Published online October 2020:eabc6599. doi:10.1126/sciadv.abc6599
  3. 3.
    You M, Fan R, Kim J, Shin S-H, Chung S. Alpha-Linolenic Acid-Enriched Butter Promotes Fatty Acid Remodeling and Thermogenic Activation in the Brown Adipose Tissue. Nutrients. Published online January 3, 2020:136. doi:10.3390/nu12010136
  4. 4.
    Campbell TC. The China Study. The China Study.

14 thoughts on “This is Your Body Temperature on Vegetable Oil”

  1. This is super interesting in that Native diets, Hawaiians and others, tended to have a very heavily starch based diet (taro, sweet potato, bread fruit, for example) yet were very lean. This part of the picture with ROS and saturated fat creation seems to be a piece of the puzzle.

  2. With the current .. actually long term problems and threats from a non-ally i.e., China, and the Corona-Virus given to USA/world, from China.. how can we intelligently and using critical thinking believe this study done in China.

    I want to believe it but, I cant. However I fo believe in thd 100% grassfed/grass-finished meats and definitely in Saturated (kidney) Fat as health giving.

    And cornstarch.. to make pancakes..?? Can we really trust that there is Non-GMO (roundup sprayed) Corn to manufacture “organic cornstarch”? I am serious.. not being negative.

    America has horrible farming practices..
    How long does it take for women to reverse and rid our fat cells of the Linoleic
    Pufa fat so we can get healthy again??

    I have used your Fire in Bottle fat when fasting or to take a tsp between meals to tide the hunger.. It kick started mg brain.. and hunger left. Took a few pieces snd swallowed water. easy.

    Would love your thoughts.

    1. The study wasn’t done by The Chinese government, it was done by Cornell Researchers. And like I say, I don’t agree with their conclusions but I have no reason to doubt the raw data.

      As to pesticides, I think that is a separate an important issue that is a bit beyond the scope of the blog. The point of the cornstarch-and-eggwhite pancakes was a theoretical one about zero PUFA foods.

      I’m glad to hear the FIAB is working for you! That’s the idea, good luck!


  3. If I do a stearic fat bomb regime with no other food intake, I suppose that I should expect an increase in my body temperature and lose my visceral fat, right?

    1. Well, perhaps. There are a lot of factors though. 1) Can you absorb pure stearic acid? Probably some, maybe not that much. 2) What is your stored body fat like. Will the “fat bomb” get absorbed at high enough rates to put the octane blend high enough and will SCD1 desaturate it as it makes it’s way to the mitochondria?


  4. The Chinese membrane fat was 20-36 omega-6. I doubt if starch eating low-fat diet could produce so much omega-6 in the stored fat.
    I think the better proxy is the MUFA content of the membrane fat. Assuming a low-pufa diet, almost all pufa ends up in membranes and very little in fat cells. So the actual saturated content of the stored fat might be membrane saturated plus membrane pufa

    1. Yeah, that’s an interesting suggestion. Membrane PUFA is always higher than stored fat, one of my future endeavors is to try to find more studies comparing the two in the same population.


  5. Interesting. I got my (first and only) test done in November of last year. I got 36.9 % saturated, 24% MUFAs, 5.26% O3 and 32.76 % O6. (1.12 % trans fats, too — not sure how, unless they are from beef.) Though I’m not “lean” by any stretch.

    So, do you think starches are “necessary” for this process? I tried eating sat fat + high starch, and went from wearing 34-36 inch pants to barely fitting into any of my 36 inch pants (gained at least 20 pounds). I found I could eat multiple croissants (made normally, with just butter), with large amounts of butter on them, with no issues. And I’d still be hungry.

    On the other hand, trying to stuff myself with your stearic acid + ghee (+ cacao butter, sometimes in a mixture) did create SOME hunger suppression. There was one time when I ate lunch and did not eat dinner (only eat 2 meals/day normally). And there were other times when I wasn’t THAT hungry at dinner, but I ate because the family was eating. Once I started eating, though, I would eat basically a normal amount. And if I ate “normal” croissants, I could just keep eating them.

    I’ve been in Twitter conversations where others also gained weight. One had the theory that if you originally gained weight by eating saturated fat + carbs, then the croissant diet did not work. I gained weight by eating a Pritikin (very low fat, high carb) diet, getting depressed, then drinking (good) beer, eating pizza, then ice cream. Circle back to Pritikin. Repeat ad nauseum. I think that’s a low PUFA diet, though at some point, I did eat some SAD.

    Any ideas on why some gain weight on the croissant diet?

    Having said all of this, I’m still eating a high saturated fat diet, including using your stearic acid. I believe it’s making me warmer, though more at night (only a sheet even though our house is at 64F) than through my body temp (always 97.5F or so). I’ve just dropped the “croissant” part off, choosing a low carb/keto + high saturated fat diet. (Losing weight again, though can’t get into my 34s and some 36s.) And there is a chance that it’s getting better over time — I seem to be eating less at my “dinner” meal now. Hard to pin that solely on sat fat, but I think it’s a factor or maybe THE factor.

    1. No, I do not think starch is necessary. But if we want to understand the real roots of obesity, I think we need to explain why it is that the French stayed lean for much of the 20th century eating a “Croissanty” diet.

      Obviously MY use of starch was initially to prove the point but then I found that it made a great vessel and helped suppress my apetite so I’m rolling with it.

      Again, I think we mostly all have some internal issues with SCD1 and PPAR gamma (look for that post soon).

      97.5 is probably a higher body temp than most Americans, but it’s still low by historical standards.

  6. I think thyroid hormones should get their due here. Possibly some thyroid disruption including possible PUFA excessive intake n6. I have a fair,y high LA according to OQ and ghastly omega ratio. Very low body temp. Now taking 1gr armour thyroid. A month later at least 1degree increase basal temp. Fatigue much decreased but appetite increased although minimal weight gain.

  7. There is a book based on The China Study called, quite imaginatively, “The China Study” by Campbell and Campbell.

    From the blurb:

    “What they found when combined with findings in Colin’s laboratory, opened their eyes to the dangers of a diet high in animal protein and the unparalleled health benefits of a whole foods, plant-based diet.”

    As with the Framingham study, people with agendas can pick out the data they like from an enormous set and make it look like a huge study backs their ideas. Even if the actual data says the opposite.

    Somehow, I doubt that the results of The China Study shows that animal proteins are dangerous and that plant-based diets have unparalleled health benefits, as this goes against just about everything I’ve learned about on the subject over the past couple of years through your work as well as through people like Saladino, Cummins, Mercola, Goodrich, and many others.

    I grabbed an ebook copy, and maybe I’ll scan through and look for some of the ‘evidence’ they use to support their assertions. Could be fun.

    1. I disagree with just about every conclusion of the authors of The Study. “The China Study” by T. Colin Campbell isn’t science, it’s propaganda. That doesn’t change the fact that the original data is very interesting.


  8. Hi Brad,

    In terms of macro content on TCD, have you seen a Law of Diminishing Returns for overall energy consumption relative to protein content for fat loss and for satiation levels? For commenters in previous posts who have trouble with plateaus during weight loss, I’m wondering if they are over-consuming energy (butter/startch) a bit beyond normal ad libidum to ‘hara hachi bu’.

    Also, as an aside, I haven’t seen anyone comment on their physical activity levels. I think routine low-aerobic threshold activity (walking, slow jogging) with occasional high-intensity bouts (sprints, heavy lifting) might fuel their fire.

    1. You may well be right about the low-aerobic activity. In terms of too many calories – yes, ultimately I believe in Calories In, Calories Out, you need to create a caloric deficit.

      I think many are being undermined in their metabolic rate by years of stored PUFA and high SCD1 activity.


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