In my previous post, I mentioned with a positive tone that I was able to increase my body temperature from 97.0 to 98.4 F. This post will explore if an increased body temperature is beneficial. I’ll start the post by sharing what others claim to be the benefit and then finish up with my own experience, as I’ve now had a higher body temperature for several years now.
The Immune System
From the article Important: Why You Need To Measure Your Body Temperature:
Body heat is needed for all sorts of vital health functions – from tissue renewal and repair to enzymatic functioning and fighting off pathogens. A warm body – as long as it’s not too hot- is a sign of a healthy thriving body.
Chronically low body temperatures is synonymous with decreased vitality and wellness and are a clear sign of a slowing metabolism. An extreme example of this is an elderly woman wrapped in jackets, beanies, gloves and scarves despite it being a hot summers day outside.
A warmer body temperature may be better for the immune system. I don’t know if this is true, but it logically makes sense. If the body needs to trigger a fever to fight off an infection, I could see it taking more energy and resources to mount that fever from a low body temperature. As we age, many will see a reduction in body temperature. And we know from the past few years that older populations are far more at risk than younger ones to fighting COVID. Could body temperature play a role?
The article Warmer body temp puts the heat on the common cold covers two studies that show a higher body temperature was more successful in fighting off illness. At cooler temperatures, immune cells were impaired.
Higher Caloric Burn
I’m leaner than I was when my body temperature was lower. Initially, I gained weight, because I was following the Ray Peat type advice to eat ice cream and drink Mexican Coke. I eventually dropped those foods. My body temp remained high, likely due to the extreme PUFA restriction (see #3 on this post).
I wanted to find out how much higher my metabolism is now. The Ace Fitness certification website teaches:
For every increase of 0.5 degrees C in internal temperature of the body, BMR increases by about 7 percent. The chemical reactions in the body actually occur more quickly at higher temperatures.
For me, that works out to about a 10% increase. That is amazing. If the average American is gaining 1.1 pounds (0.5 kg) a year, then having a 10% boost to my metabolic rate is very likely playing a role in keeping me leaner than I was when I was running at a lower temperature.
Other Claimed Benefits
I’ve seen others claim improved sleep and mood, but I didn’t find any decent supporting articles. It all seemed anecdotal. Are there other quantifiable benefits?
I always had cold hands and feet. My thyroid tests are perfectly fine. I still get feelings of cold, but not as easily. Is this a result of the higher body temperature? Maybe. I also engage in cold exposure, which likely helps me throw more heat than I did years ago. Check out the recent Getting Stronger post Benefits of Cold Adaptation or the video version for the latest information on this topic.
I don’t have detailed data, but I feel like I have fewer sick days now. Having a higher temp has not made me invincible. In early 2015, I had an upper respiratory infection that lasted a month. By that time, my body temperature was where it was at today. My last cold was in late 2019. Since then, I haven’t gotten sick with anything. This is also about the same time I restarted daily cold showers. In short, I don’t know if a higher body temp has improved my immune system. I suspect so, but I can’t prove it.
As for weight, I’ve never been leaner in my adult life. It feels easy to be this lean. I’ve maintained 180 pounds now for about 4 years now (height of 6’2.5). If I had my old body temperature back, my metabolism would be 10% slower. Staying this lean would likely require some effort.
There are longevity concerns. Am I running the flame too hot? Does a higher metabolism result in a reduced life expectancy? That is a debate that longevity experts are having now. I can see both sides of the debate. I’m partial to the argument that although higher temperatures could reduce longevity if I’m able to stay leaner and fight off infections better then that should provide at least an increased health span if not a longer life.
Overall, I will say I feel better when warmer. It is a minor effect and I have changed a lot of variables over the years, so it may be hard to parse out if it was the increased body temperature or cold exposure, or both. One interesting tidbit is that I engaged in a few years of cold exposure prior to seeing any increase in body temperature. That suggests that PUFA restriction was the main driver of increased body temp.
Photo by Matteo Fusco
Sep 15, 2022 — 8:33 am
Hi, I would like to try this but how do you accurately measure core body temperature?
Sep 20, 2022 — 11:31 pm
I love the Fire in a bottle ROS theory of a creeping obesity epidemic.
Minimized PUFA, increased starches make for intriguing reading and disquieting thoughts from this source of information.
One thing that keeps coming to mind. Would not increasing mitochondria by cardiovascular conditioning (zone 2) and let the increased processing of substrates causing the main problems be part of fixing the obesity problem as FIAB substrate manipulation theories?
Sep 21, 2022 — 9:59 am
@Vera – Accuracy is important, but if one gets measured with the same equipment at the same time of the day, seeing the variations would be more important than the raw values. Kind of like scales at the gym. Direction is the important variable.
@Marc – I can’t follow most of what FireInABottle says, but I get the big points. I will say that I did not have an increase or decrease in Zone 2 during this period. I am still lower than where I would like to be.
Sep 21, 2022 — 8:40 pm
Metabolic pathways run simultaneously. Making fat a priority to be processed metabolically efficiently would seem to be wise. Even a lean person has lots of energy stored as fat. Glycogen stored in the liver and muscles is a secondary energy supply. This fact is problematic for HIIT type training protocols, as the usage of glycogen during intense cardio can decrease glycogen storage, perhaps leading to blood glucose levels fluctuations.
Cardiovascular conditioning done slightly below Ventilatory Threshold 1 can increase fat burn at rest. Increasing the mitochondria in red twitch fibers (slow twitch) increases the ability to process fat. The slow twitch have abundant storage of and capillary activity to bring fat substrates in quickly. On the other hand, fast twitch fibers do not possess these things in the same amounts. Therefore, increasing your cardiovascular conditioning will help process fat better.
So increasing cardiovascular conditioning, high starch diets , limiting Oils, especially PUFA seems a way to easily maintain body temperature, and, get ratios of saturated fats in cells at optimal levels.
But my point is, FIAB may be overemphasizing this ROS theory to the extent that a multifaceted approach may be better overall. Sorry if I did a poor job at communicating this in my previous post.
Sep 21, 2022 — 10:25 pm
With all the recent action around CGMs and keeping glucose release as flat as possible, I’m curious how a low fat, high carb diet like yours would measure. The people over at Levels, Virta Health, and other advocates usually promote a low-carb/keto diet, though Dr Casey at Levels is mostly plant-based but eats a low-glycemic diet using lots of plant fats and fiber to keep those spikes under control. It could depend on how metabolically compromised a person is, how bad and what type of insulin resistance they are dealing with, because I’ve seen some very unhealthy people turn completely around on high carb low fat wfpb (like ray cronise), and I’ve also seen others who just cannot handle those carbs at all no matter what and get worse until they go low-carb/keto.
On a side note, I haven’t checked up on the croissant diet/Fire in a bottle folks in a while, but as of today Brad’s IG shows him to be rather obese. That doesn’t instill any confidence in me about following his diet anytime soon.
Sep 22, 2022 — 9:03 am
@Marc – Thanks for the detailed explanation.
I need to step up my Zone 2. I hate bikes. The stepper at my gym gave me quad tendonitis after 7 minutes. The only thing I can think of might be walking with a weighted vest. I always get injured when I try to jog.
@Ant – It will be interesting to see if Brad can use his knowledge to reverse his obesity. He is very open and transparent about his weight, which I respect. He also has a business that sells low PUFA meats.
If I were obese, I would do everything I could to use starchy veggies (such as cooked and cooled potatoes with vinegar) for calories. Brad is supportive of starch as a tool to reduce PUFA.
Sep 26, 2022 — 7:28 pm
FIAB briefly mentions adenosine’s role in the fat burning process. If humans could access their fat stores like a ground squirrel can during hibernation, then we would never gain much fat. However, human cannot access their fat storage on demand. Why, some may ask? Because adenosine’s role as a fat guard. Adenosine is a master regulator, and has many roles in the human body. Caffeine is an adenosine blocker. High starch meals can help, but Mother Nature is never fooled. Adenosine protects the human body from exhaustion and enables rest.
Mar 19, 2023 — 3:14 pm
I started no pufa (minimum pufa) 2 weeks ago and gained 7 pounds. Calories does matter and i have dropped carbs maximum to 100 this week instead of not couting before. I am in the “no pufa” train for the long ride.
Mar 19, 2023 — 3:23 pm
@Nancy – best of luck. I displace PUFA calories with starch.