Burning up CICO
Published 11.7.2024: I finally read Herman Pontzer’s book, Burn. And after doing so listened to a few podcasts where he discussed his work. This article I found pinned to his Twitter (or whatever it’s called when you read this).
This is the company he set up to do doubly labelled water (DLW) for the general population. In Burn, He goes over what DLW is and how they measure the calories that are burned. He goes all the way back to the inventor of DLW, who was working in mice, so the amounts were small. DLW is (still) pretty expensive, and humans need a lot more of it than mice. I think that’s (in part) the purpose behind the company, bring the costs down.
I still think his ideas are a little too clever by half… I think it IS possible to get the body to burn more calories, but I will agree that the average person does not. That was my attitude as I started the book, but I have to admit, I found his arguments hard to refute in total.
For the average person, the body seems to strive to stay at the same calorie burn. So if you exercise, the body will compensate by turning down the burn elsewhere. That’s the gist of the constrained energy model.
The model resulted from his studies of the Hazda, a tribe in Africa that (mostly) follows a hunter-gatherer lifestyle (interactions with other cultures has begun to change the tribe). They did normalize the smaller Hadza results by only considering lean body mass. Apparently fat mass is less metabolically significant. Hadza are much smaller and leaner than western humans.
I’m glad other people have issues with this point. It has ALWAYS stuck in my craw. I'm not sure that fat mass can just be ignored. Mass of all kinds requires energy to be maintained. Still unclear on this point, even after reading his book. IS fat metabolically ignorable? Everything else I’ve learned about it (that it’s basically an endocrine organ) suggests, no.
Sadly, this seems to be the only time the author of the article at the above link (Darren Dahly) addressed the issue. He now writes at Subtack. His point is that DLW is used to judge both intake and expenditure, and that the Hadza, who are much smaller, eat a lot less than Westerners. That is unaccounted for in the model. I don’t know that he mentions it in the book either. Though I’m gonna guess that the intake can also be made comparable by adjusting for size difference. Smaller people eat less (something I had to learn the hard way…)
As an aside: the same author has good advice when it comes to losing weight too. He believes in set points, which I think can be changed, though not easily or rapidly. End of Aside.
In book length, Pontzer’s points are far more persuasive. He addresses the Michael Phelps issue… in part by noting that Phelps didn’t actually eat 12,000 calories a day (I remembered the number being 10,000), but rather he probably ate about 7000 a day. Phelps himself has said that he didn’t really eat 10,000-12,000 calories a day. There is a limit as to how much the human gut (even for a really big guy like Phelps) can process in a day. This point I can accept.
The reason exercise (movement really, there’s no need to be Michael Phelps or a Tour de France racer) is important is that because calories burn is constrained, what the body does is turn down other functions in response to increased movement. Things like fidgeting, but also inflammatory actions. Inflammation requires energy, and if you use that energy in movement, then the body turns down the inflammation.
Extreme athletes cause their body to turn down other functions, such as the immune system and reproduction. Tales of female athletes having disordered menstrual cycles are common. The constrained model of metabolism also explains why athletes (he used bicyclists most often) use performance enhancing drugs (cheat) to gain an advantage. Rare is the individual who can push their body so hard… hence coaches try to “goose” the system to get more out of it.
There’s a range, obviously, so the numbers he gives in the book aren’t the same across humanity. Size matters, sex (biological sex) matters, and muscle mass matters. Hence the focus on growing muscle, a little of which can happen in the gym, but the reality is that, absent steroids, most humans aren’t going to significantly increase their muscles. Surely, I am not. But most humans (as is my goal) can work to maintain the muscle they have.
Eating less is most important when you’re talking about weight. I have no problem accepting that. It is, after all, eat less and move more. Pontzer never uses the term “set point” but he certainly walked around it consistently. His goal (having said that movement is not important in weight loss) was to indicate why exercise (movement) is still important for health. I can remember when the book came out and the headlines that blared that exercise was not important… he was, horrified.
This is the company he set up to do doubly labelled water (DLW) for the general population. In Burn, He goes over what DLW is and how they measure the calories that are burned. He goes all the way back to the inventor of DLW, who was working in mice, so the amounts were small. DLW is (still) pretty expensive, and humans need a lot more of it than mice. I think that’s (in part) the purpose behind the company, bring the costs down.
I still think his ideas are a little too clever by half… I think it IS possible to get the body to burn more calories, but I will agree that the average person does not. That was my attitude as I started the book, but I have to admit, I found his arguments hard to refute in total.
For the average person, the body seems to strive to stay at the same calorie burn. So if you exercise, the body will compensate by turning down the burn elsewhere. That’s the gist of the constrained energy model.
The model resulted from his studies of the Hazda, a tribe in Africa that (mostly) follows a hunter-gatherer lifestyle (interactions with other cultures has begun to change the tribe). They did normalize the smaller Hadza results by only considering lean body mass. Apparently fat mass is less metabolically significant. Hadza are much smaller and leaner than western humans.
I’m glad other people have issues with this point. It has ALWAYS stuck in my craw. I'm not sure that fat mass can just be ignored. Mass of all kinds requires energy to be maintained. Still unclear on this point, even after reading his book. IS fat metabolically ignorable? Everything else I’ve learned about it (that it’s basically an endocrine organ) suggests, no.
Sadly, this seems to be the only time the author of the article at the above link (Darren Dahly) addressed the issue. He now writes at Subtack. His point is that DLW is used to judge both intake and expenditure, and that the Hadza, who are much smaller, eat a lot less than Westerners. That is unaccounted for in the model. I don’t know that he mentions it in the book either. Though I’m gonna guess that the intake can also be made comparable by adjusting for size difference. Smaller people eat less (something I had to learn the hard way…)
As an aside: the same author has good advice when it comes to losing weight too. He believes in set points, which I think can be changed, though not easily or rapidly. End of Aside.
In book length, Pontzer’s points are far more persuasive. He addresses the Michael Phelps issue… in part by noting that Phelps didn’t actually eat 12,000 calories a day (I remembered the number being 10,000), but rather he probably ate about 7000 a day. Phelps himself has said that he didn’t really eat 10,000-12,000 calories a day. There is a limit as to how much the human gut (even for a really big guy like Phelps) can process in a day. This point I can accept.
The reason exercise (movement really, there’s no need to be Michael Phelps or a Tour de France racer) is important is that because calories burn is constrained, what the body does is turn down other functions in response to increased movement. Things like fidgeting, but also inflammatory actions. Inflammation requires energy, and if you use that energy in movement, then the body turns down the inflammation.
Extreme athletes cause their body to turn down other functions, such as the immune system and reproduction. Tales of female athletes having disordered menstrual cycles are common. The constrained model of metabolism also explains why athletes (he used bicyclists most often) use performance enhancing drugs (cheat) to gain an advantage. Rare is the individual who can push their body so hard… hence coaches try to “goose” the system to get more out of it.
There’s a range, obviously, so the numbers he gives in the book aren’t the same across humanity. Size matters, sex (biological sex) matters, and muscle mass matters. Hence the focus on growing muscle, a little of which can happen in the gym, but the reality is that, absent steroids, most humans aren’t going to significantly increase their muscles. Surely, I am not. But most humans (as is my goal) can work to maintain the muscle they have.
Eating less is most important when you’re talking about weight. I have no problem accepting that. It is, after all, eat less and move more. Pontzer never uses the term “set point” but he certainly walked around it consistently. His goal (having said that movement is not important in weight loss) was to indicate why exercise (movement) is still important for health. I can remember when the book came out and the headlines that blared that exercise was not important… he was, horrified.
So let’s consider fat mass…
The original Hadza paper can be found here, which Pontzer is still giving talks about. He gave one in 2021, and this guy noted that in his opinion, Pontzer’s results don’t show what he claims it does.
Basically, Pontzer considered the fat free mass (FFM) of the Hazda and Westerners and decided that the two were about the same despite the hadza moving a lot more. Hence his contention that exercise is unimportant for weight loss. It’s important for health, but not for weight loss.
This is not Pontzer’s work, but it’s related: I'm not sure how long the link will exist, it’s a preprint copy. In this case, not all people had a constrained energy out, but about half did. So in this case they were divided into responders and not. (I think that terminology is wrong). Which allows me to note another point Pontzer makes, that initially, the body will burn more in response to training or motion, but in the end, the energy burn migrates back toward it's set point (not Pontzer's word). It may be a bit elevated, but the tendency will be to go lower. Certainly, trainers do believe that as you master a particular move, your efficiency increases and the calorie burn decreases.
According to this (not a research pub in 2018) fat accounts for 3% of the total metabolism. Not a lot, but I don’t know that I’d call it negligible. But I’ve never done the measurements. Maybe 3% is under the accuracy. And based on the TEE numbers, which varied by 20%, one could be forgiven in saying the 3% from the fat is lost in the noise. No mention is made of where the 3% comes from.
This article was published in 2005, and concluded that fat mass (FM) was 6% of the metabolic total. Fat free mass (FFM) accounted for 63% of metabolism. So again, FFM >> FM, but FM is not negligible. And Westerners have WAY more fat mass than the Hadza or elite athletes like bike racers or Olympic swimmers. 2% was due to sex. Hmmm all the change in leptin was due to FM. BMR is what they measured as a stand in for metabolism.
So whether or not FM matters metabolically is not (at least in 2005) “settled” science. Different groups have gotten different results (likely using different measures)… Leptin is MADE by FM, of course ignoring that eliminates leptin as a factor. Sheesh. They did not measure BMR with doubly labeled water, but with a vent hood that measured oxygen and carbon dioxide consumption and production. Nitrogen was ignored. Nitrogen is almost always ignored, suggesting it really doesn’t affect anything. Or it suggests that no one knows how to measure it…
Basically, Pontzer considered the fat free mass (FFM) of the Hazda and Westerners and decided that the two were about the same despite the hadza moving a lot more. Hence his contention that exercise is unimportant for weight loss. It’s important for health, but not for weight loss.
This is not Pontzer’s work, but it’s related: I'm not sure how long the link will exist, it’s a preprint copy. In this case, not all people had a constrained energy out, but about half did. So in this case they were divided into responders and not. (I think that terminology is wrong). Which allows me to note another point Pontzer makes, that initially, the body will burn more in response to training or motion, but in the end, the energy burn migrates back toward it's set point (not Pontzer's word). It may be a bit elevated, but the tendency will be to go lower. Certainly, trainers do believe that as you master a particular move, your efficiency increases and the calorie burn decreases.
According to this (not a research pub in 2018) fat accounts for 3% of the total metabolism. Not a lot, but I don’t know that I’d call it negligible. But I’ve never done the measurements. Maybe 3% is under the accuracy. And based on the TEE numbers, which varied by 20%, one could be forgiven in saying the 3% from the fat is lost in the noise. No mention is made of where the 3% comes from.
This article was published in 2005, and concluded that fat mass (FM) was 6% of the metabolic total. Fat free mass (FFM) accounted for 63% of metabolism. So again, FFM >> FM, but FM is not negligible. And Westerners have WAY more fat mass than the Hadza or elite athletes like bike racers or Olympic swimmers. 2% was due to sex. Hmmm all the change in leptin was due to FM. BMR is what they measured as a stand in for metabolism.
So whether or not FM matters metabolically is not (at least in 2005) “settled” science. Different groups have gotten different results (likely using different measures)… Leptin is MADE by FM, of course ignoring that eliminates leptin as a factor. Sheesh. They did not measure BMR with doubly labeled water, but with a vent hood that measured oxygen and carbon dioxide consumption and production. Nitrogen was ignored. Nitrogen is almost always ignored, suggesting it really doesn’t affect anything. Or it suggests that no one knows how to measure it…
Bottom Line
I enjoyed the book, but do not think that I am 100% on board with the theory/model. Kevin Hall is, I believe he has already altered his energy balance model to reflect that. I am not convinced that fat mass can be completely ignored. I think it's very interesting that the fat free mass in Westerners and the Hazda agreed.
Pontzer has a second book coming out, this one is call Adaptability or Adaptable. Hopefully it doesn't take me as long to read it.
Pontzer has a second book coming out, this one is call Adaptability or Adaptable. Hopefully it doesn't take me as long to read it.