TL;DR: While I think a lot of what he says is true, there’s a lot of cognitive dissonance and a lack of information on how one can actually lose weight.
The book:
The (possibly initial) review
The good.
I think a lot of what the book says is true.
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Herman Pontzer used doubly-labeled water, which is a technique that allows one to gather calorie usage information for people (and animals, which is where he started using it). Using this, he found that the hunter-gatherer tribe the Hazda burnt about the same amount of calories per day as did normal people in sedentary jobs in the United States. While the Hazda “exercised” a lot more by walking a lot to either hunt or gather, they would then come back and sit. Their bodies adjusted for the increased calories by adjusting the calories they used elsewhere downward. It should be noted that he’s not the only one who has done this. Others have done it to compare other peoples, and the results are similar: the group that “exercised” more burnt about the same amount of carbs as the group that exercised a lot less.
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One of the more interesting sections is where he discusses the idea that exercise would increase calories burnt. That is, the common idea is the more exercise, the more calories burnt. He calls this DEE, daily energy expenditure, and divides this into physical activity and other. The common conception is that other stays the same while physical activity increases, meaning more physical activity = more DEE. His idea, however, is that there is a small increase in DEE as physical activity goes up, but then the body modifies other to go down as there is more physical activity, meaning the overall calories burnt is much smaller than what everyone thinks it is.
He uses a study of women who I think went from being sedentary to running a 1/2 marathon. While their BMR (basal metabolic rate, an estimate of what you burn just to live) stayed the same, they burnt a few more calories (expressed as DEE) when running 20 minutes a day as compared to zero. But their DEE actually goes down from there for 40 and 60 minutes of running per day. In other words, for their DEE, it was not much higher while running 60 minutes a day than doing no exercise. He also uses a mouse study with similar results.
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He thinks there’s a physical limit to the amount you can absorb. He thinks most people can only absorb about 5,000 calories a day and analyzes Michael Phelps as an example, who supposedly ate 7,000+ calories a day. There’s no way to know what he ate, though, because he never kept records. Pontzer’s theory is that perhaps Phelps was great because he could absorb more calories than “normal” people. (An aside: he says most people absorb about 95% of what they eat; My guess is that this varies depending on what you eat and by person, such that two people could eat the same diet, and one would absorb more than the other.)
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He uses some studies like the RAAM (race across America), where they start out burning 7,000 calories a day and end up near 5,000. So, it’s possible to go over your “limit” for a time, but the body reacts by lowering calories elsewhere. Although, here he thought they used so many calories and couldn’t make up the difference by absorption, so they were actually eating their own bodies.
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He thinks your energy expenditure is mainly based on weight. He has curves showing ranges of energy expenditure for body mass, and they pretty much track this idea.
I think pretty much everything he said above is true, or at least makes sense to me. I found that when I would ride my bike a lot, say 60-100 miles a week, that I would become very sparse in movement, my heart rate lowered, and I simply did less when not biking.
The bad.
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He hates Gary Taubes.
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He hates the low carb/keto diet. In one part, he discusses how great keto is for losing weight. But then says there’s a “dark side” to using fat for energy, which I found to be this argument that because the body can also use sugar, we should use sugar? It’s on pages 54-55 if you want to try to figure out what his argument is, because I can’t.
He has graphs of hunter-gatherer populations, where the higher they are in latitude, the more animals and fewer plants they eat. (And, duh! Every time someone says we should be eating a lot of plants, I think of the plants available in Connecticut in the winter: there are none or at least very few. That’s why we’d be eating meat.) But he uses this to basically say we should be eating more carbs, and he rails about the paleo and keto movements. Not a single thought is given to genetics. I’m 99.8% European, 7x% Eastern European (they change the “x” every so often due to more data). Couldn’t this mean I should be eating more meat and fewer carbs? Pontzer never goes there, always goes back to the Hazda.
- While he shows energy expenditure by weight, within a weight, there is a large difference in energy expenditure. For instance, if one weighs 200 pounds, one can burn anywhere from slightly over 2,000 calories to almost 3,500 calories. There is never an attempt (which I could find – maybe I missed one?) to determine why there is this variability (as we know exercise doesn’t create that amount of variability).
1a) He really hates Gary Taubes.
- Carb confusion. On the one hand, he says that the Hazda’s favorite food is honey, which is just sugar and water with no magical properties. And we should be eating carbs, yet lists the carb that the Hazda eat as being a very starchy root that is so starchy you spit a lot of it out. And he keeps using mainly a single group – the Hazda – to make this point that we should be eating carbs. Yet there are many groups that don’t eat carbs and do perfectly well. What if some of us can’t eat carbs? Why should we eat them?
I get the sense that Pontzer is a guy who can eat carbs and therefore doesn’t understand why anyone else can’t. He’s the guy who can eat oats for breakfast and be full for hours, whereas I’m the guy who eats oats and is physically starving 15 minutes later. Why is there no indication by Pontzer at all that maybe not everyone reacts well to carbs? There’s none, but I think it’s true. Some of us have issues with carbs.
1b) Have I told you he hates Gary Taubes? There’s a point where Pontzer goes out with a Hazda person who is gathering honey. Apparently, this guy eats a ton of honey while gathering it, and Pontzer takes a dig at Gary Taubes because of this carb intake. But (1) Gary Taubes is not saying that everyone needs to eat low carb, but some do; (2) this guy has to walk miles and risk getting stung to get carbs, so I’d eat a lot of carbs too, and I think Gary would be okay with that; (3) when is this guy going to get this much honey again, maybe never or not for a long time. And this whole idea that honey is important to the Hazda is relatively meaningless for many of us. Let that guy come to Connecticut and gather honey from wild honeybees. He’ll be dead in the winter or maybe anytime (I see incredibly few wild honeybee nests in CT).
- Cognitive dissonance. I think of cognitive dissonance as being the idea that there are two opposite ideas in your head, but both of them are true, when they can’t be. Here’s a better description:
There are so many instances of this throughout the book. Keto is a great way to lose weight; but you shouldn’t do this because of some theory about how the body uses carbs in the Krebs cycle. The Hazda eat many carbs per day, though one of their main sources is a tuber so high in starch you spit much of it out. Pontzer shows a graph of hunter gatherers where many eat a lot of meat and very few plants, yet he says we have to eat carbs. Ah, what?
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He sets up these ideas. If you exercise, your DEE doesn’t go up by much. I did not discuss this above, but he goes through studies showing if you cut back calories, your BMR (basal metabolic rate) decreases, So, exercise doesn’t do much, but cutting calories doesn’t either. And you can’t do keto, because a bunch of hunter-gatherers eat carbs so you should too. The end result is that I came away from the book without a clear idea of how to lose weight.
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He thinks we should exercise, not necessarily to lose weight, but because it’s good for us. I can’t tell what I should do with this information.
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He never delves into WHY people who weigh the same can have vastly different calorie intakes.
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He cites to basically one study where men who lost weight in a reduced calorie + exercise study kept weight off after stopping the study because they kept exercising whereas the men who stopped exercising gained their weight back. One study. Again, though, cognitive dissonance. If reducing calories causes BMR to decrease, and exercise doesn’t cause much increased calorie expenditure, how did they lose weight, and why would exercise that doesn’t cause much calorie expenditure cause people to maintain their weight loss?
I can’t find it now, but he also cites to a database where people put their own data in it. In other words, it’s self-reported. He uses this to say that people who exercise there tend to keep their weight stable. First, this is self-reported and comes with it many problems (those who self-report are more likely to be probably richer, have more time, take better care of themselves, etc., than those who don’t), and the mere fact he uses this to prove anything is suspect.
The “conclusion”.
I may write more later, but I came away from this book more confused than ever. Exercising more doesn’t mean more calories burnt, at least in the sense that running 4 miles is better than running 2 miles. You will get SOME more calories via some exercise, but it’ll be small. You can’t reduce calories because your BMR goes down. You should eat carbs and not keto, for reasons that don’t make any sense. You should exercise because it has benefits, though. (And I do think exercise has benefits, and weight loss doesn’t seem to be one of them.) But the book cover says “New research blows the lid off how we really burn calories, stay healthy, and lose weight”, but the “lost weight” part is – for my reading of the book – completely not there.
Our ultramaratoner lost quite a few kgs in days while eating 2000 kcal a day (he knew he would need a few times more but he couldn’t eat more that high). Yes, it’s extreme but the weight-loss was extreme too, it shows something. It would be very odd if some serious but more sane activity would mean NOTHING.
But it made me happier and more energetic, who knows what my hormones or other things did… Well, reducing stress easily can help with a stable weight…
I like that. (Whatever works.)
And here we are.