Calories in. Period.

Okay, to be fair, not exactly.  But, when it comes to diet and losing weight, pretty much.  So, I did a whole post on this just a few months ago referencing Herman Pontzer’s book, Burn.  And, I also mentioned some of this research in a recent quick hit (#3), but I actually read Burn last week and it was so, so good.  

First of all, Pontzer is a professor who writes like a science journalist.  So readable and engaging.  Also, he’s an evolutionary anthropologist, so the evolutionary lens through which he approaches all of this is fascinating.  I also loved little tidbits like how many calories are expended in each heartbeat (1/300th a calorie) and how humans lacking modern sanitation burn way more calories on their immune system.  And, yeah, I posted before about how little control you have over the calories out, but it really got through to me in reading this book.  Like the fact that the hunter/gatherer Hadza who walk miles and miles every day actually burn no more calories than your average American coach potato! Really.  

So, yes, of course calories out matters.  It’s just that you have almost no control over those.  And, of course, a ton of control over calories in.  The part about diet and nutrition was not necessarily all that new to me, but a great synthesis of knowledge on this subject.  Like, whatever diet allows you to consume a level of calories in consistent with your typical calories out where you are getting the nutrients you need and not feeling hungry is a good diet.  And I really loved the rule of thumb that, basically, the fat you ingest should come with protein and the carbs you ingest should come with fiber.  

Anyway, if you find this stuff interesting at all, you really should check out the book.  And here’s some good stuff from a Q&A:

Q: What’s the biggest misunderstanding about human metabolism?

A: We’re told — through fitness magazines, diet fads, online calorie counters — that the energy we burn each day is under our control: if we exercise more, we’ll burn more calories and burn off fat. It’s not that simple! Your body is a clever, dynamic product of evolution, shifting and adapting to changes in our lifestyle.

Q: In your book you say we’re driven to magical thinking when it comes to calories. What do you mean by that?

A: Because our body is so clever and dynamic, and because humans are just bad at keeping track of what we eat, it’s awfully hard to keep track of the calories we consume and burn each day. That, along with the proliferation of fad diets and get-thin-quick schemes, has led to this idea that “calories don’t matter.” That’s magical thinking. Every ounce of your body — including every calorie of fat you carry — is food you consumed and didn’t burn off. If we want to lose weight, we must eat fewer calories than we burn. It really comes down to that.

Q: Some people say that if the cavemen didn’t eat it, we shouldn’t either. What does research show about what foods are “natural” for humans to eat?

A: There’s no singular, natural human diet. Hunter-gatherers like the Hadza eat a diverse mix of plant and animal foods that varies day to day, month to month, and year to year. There’s even more dietary diversity when we look across populations. Humans are built to thrive on a wide variety of diets — just about everything is on the menu.

That said, the ultra-processed foods we’re inundated with in our modern industrialized world really are unnatural. There are no Twinkies to forage in the wild. Those foods are literally engineered to be overconsumed, with a mix of flavors that overwhelm our brain’s ability to regulate our appetites. Now, it is still possible to lose weight on a Twinkie diet (I’m not recommending it!), if you’re very strict about the calories eaten per day. But we need to be really careful about how we incorporate ultra-processed foods into our daily diets, because they are calorie bombs that drive us to overconsume.

Q: If we could time travel, what would our hunter-gatherer ancestors make of our industrialized diet today?

A: We don’t even need to imagine — We are those hunter-gatherers! Biologically, genetically, we are the same species that we were a hundred thousand years ago, when hunting and gathering were the only game in town. When we’re confronted with modern ultra-processed foods, we struggle. They are engineered to be delicious, and we tend to overconsume.

About Steve Greene
Professor of Political Science at NC State

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