Excercised - A review at last
Published 7.15.2025: Yes, I finally finished the book, Exercised by Daniel Lieberman. Actually I finished it in mid-May, but this is when the review made it into the pipeline. Bottom line: this book is worth reading.
Part of the reason I read this book was that I saw a talk and interview with him on the YouTube Channel Viva Longevity (formerly Plant Chompers), which has changed its focus from veganism to longevity, which tends to be supported by a whole foods plant based diet— though not necessarily veganism.
Anyway, Lieberman was the advisor of Herman Pontzer when he was at Harvard. In his book, Lieberman’s thesis is that humans did NOT evolve to exercise, and observing the Hazda proves this. The reason I started writing this though is that in part I of his book, Pontzer states that people with larger fat stores (westerners) use more energy to live BUT that the fat mass is not metabolically important. I am still stuck on this factoid, which seems to be universally accepted, but which I cannot square the circle about.
It doesn’t make any sense to me that fat plays no metabolic role. I do get why researchers normalize fat mass away, westerners don’t have less fat free mass than the Hazda, they just have a LOT more fat mass. I just don’t (can’t?) think the fat mass plays no role metabolically.
Fat mass DOES play a role, westerners expend a lot more energy to move than the much lighter Hazda, and I’m sure we have higher inflammation. Aren’t those metabolic? So, so confused…. Of course, it also makes sense that fat cells (full of stored energy) would not need the body to provide any further energy to them. Maybe that’s the reason?
Lieberman shows a graph, using Pontzer's data, and in that graph he shows that the Hazda CLEARLY expend more energy than westerners… and the difference is starker when you divide by fat free mass. The difference is about 20%, but that's huge. It's 27 calories/kg for Hazda and 18 calories/kg for westerners. That NOT negligible!!
Lieberman is focused on the comparison with chimpanzees, but his westerner data is different than Pontzer's. Even his physical activity level (PAL) data show the Hazda are much more active than sedentary westerners. Sedentary westerners PAL is similar to chimpanzees.
I'm very glad that I read this book second. His focus is humans and evolution, but I think he put the lie to Pontzer's work. He definitely seems to counter Pontzer. People can lose weight through exercise, and adding twice the amount of steps doesn't mean that the body compensates.
Lieberman does note that different peoples burn the same amount of energy (within a WIDE range). I'm less convinced about the constrained energy model— certainly I have taken steps to up my NEAT— And I don't buy the idea that anythings done consciously is therefore not NEAT (which stands for non-exercise activity thermogenesis).
At least Lieberman allows that Pontzer's theory is controversial. Not sure he's on board with the theory, but this book is really not about that. It is, however, why I read the book— which is why I've spent so much time on what is really a minor portion of the book.
Lieberman is apparently the guy who popularized barefoot running. Though he admits that it's not for everyone. This came out of the idea (also promoted in a book) that humans were born to run. Well, if that's the case, why do so many get injured when running? He claims that injuries that are a U curve. New runners tend to get injured, and people who've been doing it awhile and running many, many miles a day.
Exercise is good for aging, or at least makes aging happen more slowly… he does not pretend that everyone doesn't die and fail in the end. That exercise is good for aging is actually not news to me, and it's not clear that he originated it. Still, exercise both causes damage to the muscles, but also allows the body to heal and "clean up" itself.
But exercise is NOT natural… so his focus is how to make exercise less objectionable. Because not everybody wants to run or go to the gym.
Obesity has been considered a disease since 2013. Lieberman does think that exercise can lead to weight loss, but it needs to be vigorous and it won't offset a bad diet (which still varies from Pontzer).
Better to do a short vigorous cardio than longer term moderate exercise, but it all helps. As a runner, Lieberman's big on cardio— need to do more than weights, at least if you want cholesterol and high blood pressure results. This book made me glad I started doing dedicated cardio twice a week— though I'm part of his U curve of injuries.
As an aside to the above mentioned cardio: I used to be a runner… but that was about 40 years ago. I never did learn how to really warm up my muscles and joints before running, and lately that has bitten me in the ass. Back in the day, my issues were with my heels, but altering my gait helped with those. Now it's me knees. Interestingly, my dietitian in training daughter thought it was related to my over tight quads— which is an issue of not warming up properly. She may be correct. End aside.
The reason I wanted to read this book was, yes the podcast where I saw him speak, but also the contra data to Pontzer's book. Pontzer has another book out where I think he addresses some of the points made by others, but I have read to read that one. This book is rigorously cited and very much worth a read.
DISCLAIMER: I am NOT any type of medical professional. Do NOT take medical advice from me!!
Part of the reason I read this book was that I saw a talk and interview with him on the YouTube Channel Viva Longevity (formerly Plant Chompers), which has changed its focus from veganism to longevity, which tends to be supported by a whole foods plant based diet— though not necessarily veganism.
Anyway, Lieberman was the advisor of Herman Pontzer when he was at Harvard. In his book, Lieberman’s thesis is that humans did NOT evolve to exercise, and observing the Hazda proves this. The reason I started writing this though is that in part I of his book, Pontzer states that people with larger fat stores (westerners) use more energy to live BUT that the fat mass is not metabolically important. I am still stuck on this factoid, which seems to be universally accepted, but which I cannot square the circle about.
It doesn’t make any sense to me that fat plays no metabolic role. I do get why researchers normalize fat mass away, westerners don’t have less fat free mass than the Hazda, they just have a LOT more fat mass. I just don’t (can’t?) think the fat mass plays no role metabolically.
Fat mass DOES play a role, westerners expend a lot more energy to move than the much lighter Hazda, and I’m sure we have higher inflammation. Aren’t those metabolic? So, so confused…. Of course, it also makes sense that fat cells (full of stored energy) would not need the body to provide any further energy to them. Maybe that’s the reason?
Lieberman shows a graph, using Pontzer's data, and in that graph he shows that the Hazda CLEARLY expend more energy than westerners… and the difference is starker when you divide by fat free mass. The difference is about 20%, but that's huge. It's 27 calories/kg for Hazda and 18 calories/kg for westerners. That NOT negligible!!
Lieberman is focused on the comparison with chimpanzees, but his westerner data is different than Pontzer's. Even his physical activity level (PAL) data show the Hazda are much more active than sedentary westerners. Sedentary westerners PAL is similar to chimpanzees.
I'm very glad that I read this book second. His focus is humans and evolution, but I think he put the lie to Pontzer's work. He definitely seems to counter Pontzer. People can lose weight through exercise, and adding twice the amount of steps doesn't mean that the body compensates.
Lieberman does note that different peoples burn the same amount of energy (within a WIDE range). I'm less convinced about the constrained energy model— certainly I have taken steps to up my NEAT— And I don't buy the idea that anythings done consciously is therefore not NEAT (which stands for non-exercise activity thermogenesis).
At least Lieberman allows that Pontzer's theory is controversial. Not sure he's on board with the theory, but this book is really not about that. It is, however, why I read the book— which is why I've spent so much time on what is really a minor portion of the book.
Lieberman is apparently the guy who popularized barefoot running. Though he admits that it's not for everyone. This came out of the idea (also promoted in a book) that humans were born to run. Well, if that's the case, why do so many get injured when running? He claims that injuries that are a U curve. New runners tend to get injured, and people who've been doing it awhile and running many, many miles a day.
Exercise is good for aging, or at least makes aging happen more slowly… he does not pretend that everyone doesn't die and fail in the end. That exercise is good for aging is actually not news to me, and it's not clear that he originated it. Still, exercise both causes damage to the muscles, but also allows the body to heal and "clean up" itself.
But exercise is NOT natural… so his focus is how to make exercise less objectionable. Because not everybody wants to run or go to the gym.
Obesity has been considered a disease since 2013. Lieberman does think that exercise can lead to weight loss, but it needs to be vigorous and it won't offset a bad diet (which still varies from Pontzer).
Better to do a short vigorous cardio than longer term moderate exercise, but it all helps. As a runner, Lieberman's big on cardio— need to do more than weights, at least if you want cholesterol and high blood pressure results. This book made me glad I started doing dedicated cardio twice a week— though I'm part of his U curve of injuries.
As an aside to the above mentioned cardio: I used to be a runner… but that was about 40 years ago. I never did learn how to really warm up my muscles and joints before running, and lately that has bitten me in the ass. Back in the day, my issues were with my heels, but altering my gait helped with those. Now it's me knees. Interestingly, my dietitian in training daughter thought it was related to my over tight quads— which is an issue of not warming up properly. She may be correct. End aside.
The reason I wanted to read this book was, yes the podcast where I saw him speak, but also the contra data to Pontzer's book. Pontzer has another book out where I think he addresses some of the points made by others, but I have read to read that one. This book is rigorously cited and very much worth a read.
DISCLAIMER: I am NOT any type of medical professional. Do NOT take medical advice from me!!