Herman Pontzer

Excited to announce my new book ADAPTABLE coming this Spring!

Huh, I wonder what changed in early 2025?

@Gonzalez_JT @Brady_H Ok, but if a person gains 2 kg of fat free mass, we expect their RMR to increase. If the observed change is 0, then that’s compensation (or find another word for it). Same if tx gains 2 kg FFM > control group. The tx is expected to increase FFM and RMR. Need to account for that

@HermanPontzer @Brady_H You mean the meta-analysis of RCTs? Adjusting for covariates post-randomisation is ill advised as it can introduce bias. Randomisation provides the least biased estimates of causal effects. Without a randomised control group, apparent effects can reflect confounding

Does exercising more lead to lower resting energy expenditure (“metabolic compensation”)? Maybe not. When people increased their physical activity energy expenditure by ~250 calories/day, their *total* daily energy expenditure also increased by 10% (272 calories/day). “…contradicting the hypothesis that metabolic compensation thwarts the effects of physical activity on weight management.”

@Gonzalez_JT @Brady_H We found evidence after ~15 weeks once you control for changes in fat free mass and separate resistance from endurance training. (The review paper you cite did neither) cell.com/current-biolog…

@HermanPontzer @Brady_H And no evidence from RCTs even up to 24 weeks, with supervised exercise

@Gonzalez_JT @Brady_H Maybe but no one has ever claimed that compensation to exercise happens that fast. In our 2019 Curr Bio study (Thurber) the 1st week of high output showed 0 compensation.

@HermanPontzer @Brady_H In contrast to energy deficit, the evidence for reduced RMR in response to increased physical activity is very weak pubmed.ncbi.nlm.nih.gov/42386238/ sciencedirect.com/science/articl…

@JYKines Thats deep bro. I’m referring to the fact that we collectively know a lot more about how the universe works in pretty much every field than we did, say, 10…50…100 years ago.

@HermanPontzer What does science move forward towards, and how do you know with certainty?

Science moves forward. That was 10 years ago. Here’s the updated model and data: cell.com/current-biolog…

@bozavlado I did a full detailed thread when the paper came out. Happy to share a pdf - send me an email

@HermanPontzer I can pay for open access fees even with Slovak tiny grant money. What are you doing here? Sharing paywalled research? At least give us a thread with main points...

@1NF1N173CU17UR3 We checked that - no evidence of exercise efficiency increase in the studies we found for the review.

@HermanPontzer Wouldn’t this just be due to your body being more efficient given increased exercise? Like, someone untrained running has a higher heart rate vs a runner at the same weight and speed.

@AmirFFT @GavinRayDev @dantawfik @DrLeanneRedman Glad you’ve got it figured out!

seems like a modality specific compensation masquerading as general(ized) constraint on all forms of exercise. human energy expenditure may not be simply and linearly additive, but it is constrained in that way either. It is adaptive, modality-dependent, and strongly influenced by energy availability (HOW the deficit is achieved - input reduction or output increase - then the nature of the output etc)

Exercise burns 500 extra calories. Your body compensates by spending 500 fewer. Net change: zero. A foundational study by @HermanPontzer measuring 332 adults across five populations proved the math behind weight loss doesn't work the way we've been told. Ponzer and his team used doubly labeled water to measure total energy expenditure and accelerometry to track physical activity in adults from Ghana, South Africa, Seychelles, Jamaica, and the United States. This method captures actual metabolic rate over 7-10 days in free-living conditions, not lab-based estimates. The standard additive model predicts that total energy expenditure increases linearly with physical activity. Burn 200 more calories moving, spend 200 more calories total. That's the assumption underlying most weight loss and obesity prevention strategies. The data revealed something different. After adjusting for body size and composition, total energy expenditure was positively correlated with physical activity at low-to-moderate activity levels. But in subjects with higher physical activity levels, total energy expenditure plateaued. The relationship wasn't linear. It was constrained. This supports a constrained total energy expenditure model: the body adapts metabolically to maintain total energy expenditure within a narrow range when physical activity increases beyond moderate levels. The metabolic response to activity isn't passive addition. It's active compensation. Two variables appeared to modulate this response: body fat percentage and activity intensity. Higher body fat was positively related to total energy expenditure, while higher activity intensity was inversely related to total expenditure after controlling for activity volume. The body's adaptive mechanisms aren't uniform across metabolic phenotypes. The compensation mechanisms likely involve reductions in basal metabolic rate, thermic effect of food, or non-exercise activity thermogenesis. When physical activity energy expenditure increases substantially, other components of daily energy expenditure decrease to keep total expenditure stable. This has direct implications for weight loss interventions. Exercise programs that substantially increase physical activity may not produce the caloric deficits predicted by additive models because the body compensates by reducing energy expenditure elsewhere. The expected 1:1 relationship between activity and expenditure breaks down at higher activity levels. The plateau doesn't mean exercise is ineffective. Physical activity produces metabolic benefits independent of energy balance, including improved insulin sensitivity, mitochondrial function, and cardiovascular health. But using exercise as the primary driver of caloric deficit faces a biological constraint that most public health models don't account for. The constrained model also explains why cross-population studies consistently find that more active populations don't have proportionally higher total energy expenditure. If compensation occurs above moderate activity levels, highly active hunter-gatherer populations and sedentary Western populations can show similar total daily energy expenditure despite vastly different activity patterns. The decisions about exercise intensity, volume, and metabolic context (body composition, dietary intake) interact with constrained energy expenditure in ways that aren't captured by simple calorie-counting models. The body regulates total energy expenditure as a managed system, not a passive ledger. Public health strategies built on additive energy expenditure models assume a biological response that doesn't match observed physiology. The constrained total energy expenditure framework suggests that preventing weight gain requires addressing both sides of energy balance, and that increasing activity alone may not produce the metabolic effects predicted by conventional models.

@AmirFFT @GavinRayDev @dantawfik @DrLeanneRedman Meh. Lots of evidence for energy constraint. Here’s the 10-yrs updated science: cell.com/current-biolog…

@GavinRayDev @dantawfik @HermanPontzer @DrLeanneRedman Bingo

Two of the most important biomedical breakthroughs came from science of the Gila lizard venom (GLP-1s) and yogurt (CRISPR genome editing). "The system that turned that lizard into a medicine is now being dismantled." "Less support for scientists means strange questions no one will get to chase." gift link nytimes.com/2026/06/20/opi…

The humiliating Iran deal requires the U.S. to come up with a $300 billion reparations payment to Iran. That's more than Iran's entire GDP. Trump says taxpayers won't pay for it. 1/ So I compiled a helpful list.

It’s funny, motocross at the White House is, like, fine with me. But here’s an example of something that is genuinely unforgivable but that a lot of people seem to have moved right past.

2016 Falcons feeling pretty good about themselves today

Fun human evolution connection: vitamin A poisoning likely killed a H erectus female 1.7 million years ago (they didn’t have twitter docs to save them) humanorigins.si.edu/evidence/human…

!!Announcing the next round of Isotope Grants for DLW projects!! Successful proposals get free isotopically enriched water for human DLW studies. Proposals due Sept 1. Details & application here: sites.duke.edu/pontzerlab/dlw…

Honored to be elected a @aaas Fellow! More important than ever to promote solid science and communicate it widely. trinity.duke.edu/news/duke-prof…

In this episode, evolutionary anthropologist Dr. Herman Pontzer (@HermanPontzer) of the world's leading researchers on human metabolism and energy expenditure at Duke University—joins the show to share what decades of fieldwork with the Hadza hunter-gatherers of Tanzania have revealed about how our bodies really work. We explore what hunter-gatherers actually eat (spoiler: it's not the all-meat paleo diet you've been sold), why the healthiest hearts ever measured belong to a community whose staple foods are unrefined carbohydrates, and the shocking finding that the Hadza—despite walking up to 19,000 steps a day—burn no more calories than sedentary Americans. Dr. Pontzer explains his groundbreaking "constrained energy" model and why your body quietly reallocates energy from inflammation, stress hormones, and reproductive functions when you exercise more, rather than simply burning extra fuel. We also dive into Dr. Pontzer's landmark Science paper on metabolism across the human lifespan, which upends the popular belief that a slowing metabolism causes middle-age weight gain. The data from over 6,000 people show that your metabolic rate holds remarkably steady from your mid-20s all the way into your late 50s—meaning diet, not metabolism, is what's really driving the obesity crisis. Dr. Pontzer shares practical takeaways: prioritize minimally processed foods, get your fiber and protein, and stop blaming your metabolism for weight gain. The conversation closes with a powerful reflection on what modern life has lost—community, presence, and a healthier relationship with time—drawn from his years living among the Hadza. Dr. Pontzer also introduces his new book Adaptable, a guide to understanding human biology through the lens of evolution. Timestamps 00:00 Introduction to Human Metabolism and Energy Expenditure 02:35 Hunter-Gatherer Diets: What Do They Really Eat? 09:38 The Role of Honey in the Hadza Diet 10:25 Translating Evolutionary Diets to Modern Contexts 12:14 Health Status of Hunter-Gatherers 14:50 Lipid Profiles and Heart Health in Hunter-Gatherers 19:26 Adaptations of Arctic Diets: The Inuit Example 21:45 Variability in Animal Source Foods Among Hunter-Gatherers 24:29 Debunking Dietary Myths 29:11 Energy Expenditure and the Hadza 32:58 Metabolism Across the Lifespan 42:07 Nutritional Insights from Hunter-Gatherers 47:14 Lessons from the Hadza: Community and Time 50:14 Introducing 'Adaptable': Understanding Human Biology

@dietiti3n @TyBealPhD Yes that could definitely contribute. The analyses we’re discussing here hold LBM constant so we can compare across people of different sizes. But in absolute terms, lower LBM will lead to lower energy expenditure per day.

@TyBealPhD @HermanPontzer What about LBM loss over that time frame? Could this be a reason for perceived metabolic rate lowering ?

I turned 40 today and my metabolism is not slowing down. @HermanPontzer explains the real reason why we gain weight in middle age.