Burn by Herman Pontzer

Pontzer, H. (2021) Burn: The Misunderstood Science of Metabolism. Allen Lane [publisher site]

I've recently enjoyed reading Dan Lieberman's book, Exercised and in doing so realised it was the first time that I'd looked into the evolutionary perspectives on physical activity with any real depth. Soon afterwards I received a copy of Katy Tapper's excellent new Health Psychology and Behaviour Change textbook and having just tuned into the topic myself really enjoyed the whole chapter she had devoted to evolutionary and historical determinants of health, a topic that I'd not noticed before in any similar textbooks. I contacted Katy to congratulate her on the book and she also recommended another new title in the same field which I was inspired by and have now read. That book was Burn by Pontzer and this page is my brief summary and page of related links.

Herman Pontzer is an evolutionary anthropologist working in a similar space to Dan Lieberman (Lieberman was Pontzer's advisor for his PhD) and just as Lieberman has studied a number of contemporary hunter-gatherer tribes such as the Hadze, the Tsimane and Shuar's, Pontzer also contends that in order to gain useful perspective on the optimal design features of our modern selves we should be examining the data that tells us about our evolutionary past; archaeological fossil records, ethnographies of living hunter-gatherers, and analysis of the human genome. The difference between Lieberman's and Pontzer's books are that the latter book examines these issues from the perspective of human metabolism and makes the case that this is at the heart of what separates humans from our closest animal relatives.

Pontzer contends that in order to understand how a species lives it's life we need to understand how it chooses to use it's energy; where it prefers to get it's energy from and how it manages energy storage and release in times of plenty and times of need. The book explains what metabolism is and it's relationship with our diet, our physical activity needs, extreme human endurance, and energy consumption from a broader perspective. A main theme in the book is to outline how difficult it is to accurately measure Total Energy Expenditure and it's clear that Pontzer was one of the first researchers to use doubly labelled water techniques to accurately analyse the daily energy expenditures of hunter-gatherer people.

It's these gold standard research methods that have underpinned another concept in the book, that of a "Constrained Daily Energy Expenditure". This is the idea that there are limits to how much we can increase our metabolism (Pontzer et al , 2016; Pontzer, 2018; Urlacher et al , 2019; Thurber et al, 2019) and in the case of Pontzer's hunter-gatherer studies, "results from the hadza seemed to fly in the face of the factorial approach to estimating daily energy expenditure which assumes that daily energy expenditure increases in response to daily physical activity" (p 160). Pontzer says that the "armchair engineer" models of metabolism are additive in contending that daily energy expenditure continues to rise with increasing levels of physical activity whereas studies of these highly active tribes suggest that the body adapts dynamically and is self-limiting in how much energy it chooses to spend on physical activity.

This theory in turn underpins the concept that more exercise does not always mean increased weight loss as more exercise does not necessarily mean the creation of a calorific deficit. This is in line with the idea that one "can't outrun a bad diet" and while the publicity for the book may pitch this as a new idea that runs against accepted wisdom there are many people who are well aware of this; once we look past the simplified views of the extreme and vocal people on social media. While I think it is widely known, at least in professional circles, that exercise alone will not lead to optimal weight loss, there is however a knowledge gap as to exactly why this is the case. I would suggest that the predominant response would be that more exercise leads to increased appetite and subsequent intake whereas this metabolic adjustment theory of constrained daily energy expenditure would add another perspective to the understanding of many.

This insight sounds like it's starting to align in support of many in the LCHF/paleo world whose central beliefs are often all about diet over exercise for weight loss and who often attack Calories In, Calories Out as a flawed concept. This field of evolutionary research has clearly been used to underpin a range of diets and lifestyle advice, most notably the paleo movement but Pontzer's perspective is that we have evolved as "opportunistic omnivores", and along the way he includes a short but withering critique of the extreme ends of both the paleo and vegan movements. Pontzer highlights how Loren Cordain's work has been used to underpin much of the core rationale however Pontzer describes the limitations in the original methodology when Cordain tried to summarise the hunter-gatherer diets. Cordain did not go to observe the hunter-gatherers himself instead relying on Murdock's Atlas, a large scale anthropological database that failed to include women's diets, ignored vast amounts of honey that were often consumed, reported averages rather than the range of food consumed, and which Murdoch himself had "no hesitation in rejecting the validity and utility" of later in life. Pontzer also points out that some examples of hunter-gatherer populations are not really what they appear to be and have in reality, far from being hunter-gatherers, been pastoralists or much younger communities. More recent descriptions of hunter-gatherer life (e.g. see Raichlen et al, 2017) have shown that there are much higher levels of carbohydrates being consumed and these are shown against two of the classic paleo diet pillars of research in the diagram shown below from p203. It's this sort of forensic but well communicated insight that will no doubt upset many who have fashioned their identities and/or income streams around the idea that ancient man never ate carbohydrates (and I use the word 'man' purposefully here because they rarely seem to talk about women).

There's a chapter on high performance sport and exercise which is interesting for those whose interests range across the spectrum from sport to health and once again, Pontzer uses a range of insight and research to show how it's more complicated than a direct correlation between exercise and increased metabolism with one example being how the body clearly makes adaptations over many years of being physically active to reduce levels of hormones in the body (e.g. testosterone, see Hackney, 2020).

I found the book enlightening when thinking about both exercise and nutrition for health and for giving perspective on high-performance training considerations. I found the final chapter on broader thoughts on energy consumption and the link with fossil fuels and the environment a bit out of kilter with the rest of the book albeit an important topic and clearly connected in some ways.

On this page I've included some of the references and science that most interested me along with a few interviews that Dr Pontzer has conducted alongside the book release. If you found any of this useful please let me know @benjanefitness.

Watch a Video

Listen to a podcast

Woods, A. and Martin, M.(2021) "Episode 059: Feel the burn: The limits of human energy expenditure and endurance". BigBiology Podcasts. 60. https://scholarworks.umt.edu/bigbiology_podcasts/60

Selected References

Dugas, L. R., Harders, R., Merrill, S., Ebersole, K., Shoham, D. A., Rush, E. C., ... & Luke, A. (2011). Energy expenditure in adults living in developing compared with industrialized countries: a meta-analysis of doubly labeled water studies. The American journal of clinical nutrition, 93(2), 427-441. https://doi.org/10.3945/ajcn.110.007278

Hackney, A. C. (2020). Hypogonadism in exercising males: dysfunction or adaptive-regulatory adjustment?. Frontiers in endocrinology, 11, 11. https://doi.org/10.3389/fendo.2020.00011

Hall, K. D., Ayuketah, A., Brychta, R., Cai, H., Cassimatis, T., Chen, K. Y., ... & Zhou, M. (2019). Ultra-processed diets cause excess calorie intake and weight gain: an inpatient randomized controlled trial of ad libitum food intake. Cell metabolism, 30(1), 67-77. https://doi.org/10.1016/j.cmet.2019.05.008

Lister, A. M. (2014). Behavioural leads in evolution: evidence from the fossil record. Biological Journal of the Linnean Society, 112(2), 315-331. https://doi.org/10.1111/bij.12173

Pontzer, H. (2017). The crown joules: energetics, ecology, and evolution in humans and other primates. Evolutionary Anthropology: Issues, News, and Reviews, 26(1), 12-24. https://doi.org/10.1002/evan.21513

Pontzer, H. (2018). Energy constraint as a novel mechanism linking exercise and health. Physiology, 33(6), 384-393. https://doi.org/10.1152/physiol.00027.2018

Pontzer, H., Durazo-Arvizu, R., Dugas, L. R., Plange-Rhule, J., Bovet, P., Forrester, T. E., ... & Luke, A. (2016). Constrained total energy expenditure and metabolic adaptation to physical activity in adult humans. Current Biology, 26(3), 410-417. https://doi.org/10.1016/j.cub.2015.12.046

Pontzer, H., Raichlen, D. A., Gordon, A. D., Schroepfer-Walker, K. K., Hare, B., O’Neill, M. C., ... & Ross, S. R. (2014). Primate energy expenditure and life history. Proceedings of the National Academy of Sciences, 111(4), 1433-1437. https://doi.org/10.1073/pnas.1316940111

Pontzer, H., Brown, M. H., Raichlen, D. A., Dunsworth, H., Hare, B., Walker, K., ... & Ross, S. R. (2016). Metabolic acceleration and the evolution of human brain size and life history. Nature, 533(7603), 390-392. https://doi.org/10.1038/nature17654

Pontzer, H. (2017). Economy and endurance in human evolution. Current Biology, 27(12), R613-R621. https://doi.org/10.1016/j.cub.2017.05.031

Pontzer, H., Wood, B. M., & Raichlen, D. A. (2018). Hunter‐gatherers as models in public health. Obesity Reviews, 19, 24-35. https://doi.org/10.1111/obr.12785

Raichlen, D. A., Pontzer, H., Harris, J. A., Mabulla, A. Z., Marlowe, F. W., Josh Snodgrass, J., ... & Wood, B. M. (2017). Physical activity patterns and biomarkers of cardiovascular disease risk in hunter‐gatherers. American Journal of Human Biology, 29(2), e22919. https://doi.org/10.1002/ajhb.22919

Swift, D. L., Johannsen, N. M., Lavie, C. J., Earnest, C. P., & Church, T. S. (2014). The role of exercise and physical activity in weight loss and maintenance. Progress in cardiovascular diseases, 56(4), 441-447. https://doi.org/10.1016/j.pcad.2013.09.012

Thurber, C., Dugas, L. R., Ocobock, C., Carlson, B., Speakman, J. R., & Pontzer, H. (2019). Extreme events reveal an alimentary limit on sustained maximal human energy expenditure. Science Advances, 5(6), eaaw0341. https://doi.org/10.1126/sciadv.aaw0341

Urlacher, S. S., Snodgrass, J. J., Dugas, L. R., Sugiyama, L. S., Liebert, M. A., Joyce, C. J., & Pontzer, H. (2019). Constraint and trade-offs regulate energy expenditure during childhood. Science advances, 5(12), eaax1065. https://doi.org/10.1126/sciadv.aax1065

Yang, J., Christophi, C. A., Farioli, A., Baur, D. M., Moffatt, S., Zollinger, T. W., & Kales, S. N. (2019). Association between push-up exercise capacity and future cardiovascular events among active adult men. JAMA network open, 2(2), e188341-e188341.

Further Reading

Berbesque, J. C. (2010). Sex differences in food preferences, eating frequency, and dental attrition of the Hadza.

Williams, S (2019) Metabolism Hits a Ceiling in Athletic Endurance Feats https://www.the-scientist.com/news-opinion/human-endurance-constrained-by-metabolism--runners-study-65971

Hare, B. (2017). Survival of the friendliest: Homo sapiens evolved via selection for prosociality. Annual review of psychology, 68, 155-186. https://doi.org/10.1146/annurev-psych-010416-044201

Zuk, M. (2013). Paleofantasy: What evolution really tells us about sex, diet, and how we live. WW Norton & Company.

Pontzer, H. (2021). Metabolism myths. New Scientist, 249(3323), 32-36. https://doi.org/10.1016/S0262-4079(21)00332-8

Also on this website

A similar book review on this website: Exercised by Dan Lieberman.