Calories IN. Calories out.

As you know, I’m a big fan of the “calories in, calories out” approach to weight control/loss.  It’s definitely worked for me.  And I’ve long understood that, as much as I am committed to exercise, the key really is substantial reduction in the calories in portion of the equation.  Thanks, I think, to DJC who sent me this article that is, even given what I’ve recognized, pretty depressing on the calories out score.  But, also, pretty fascinating on the marvel of evolution that are human bodies are– even if it makes a bad match for modern society:

Every minute, everything the body does—growing, moving, fighting infection, even just existing—”all of it takes energy,” says Pontzer, a professor at Duke University.

In his new book, Burn (Avery, 2021), the evolutionary anthropologist recounts the 10-plus years he and his colleagues have spent measuring the metabolisms of people ranging from ultra-athletes to office workers, as well as those of our closest animal relatives, and some of the surprising insights the research has revealed along the way.

Much of his work takes him to Tanzania, where members of the Hadza tribe still get their food the way our ancestors did—by hunting and gathering. By setting out on foot each day to hunt zebra and antelope or forage for berries and tubers, without guns or electricity or domesticated animals to lighten the load, the Hadza get more physical activity each day than most Westerners get in a week.

So they must burn more calories, right? Wrong.

Pontzer and his colleagues have found that, despite their high activity levels, the Hadza don’t burn more energy per day than sedentary people in the US and Europe.

These and other recent findings are changing the way we understand the links between energy expenditure, exercise, and diet. For example, we’ve all been told that if we want to burn more calories and fight fat, we need to work out to boost our metabolism. But Pontzer says it’s not so simple.

“Our metabolic engines were not crafted by millions of years of evolution to guarantee a beach-ready bikini body,” Pontzer says. But rather, our metabolism has been primed “to pack on more fat than any other ape.” What’s more, our metabolism responds to changes in exercise and diet in ways that thwart our efforts to shed pounds.

What this means, Pontzer says, is you can walk 16,000 steps each day like the Hadza and you won’t lose weight. Sure, if you run a marathon tomorrow you’ll burn more energy than you did today. But over time, metabolism responds to changes in activity to keep the total energy you spend in check.

Here, Pontzer explains his book and some surprising myths about metabolism:


What’s the lesson the Hadza and other hunter-gatherers teach us about managing weight and staying healthy?


The Hadza stay incredibly fit and healthy throughout their lives, even into their older ages (60’s, 70’s, even 80’s). They don’t develop heart disease, diabetes, obesity, or the other diseases that we in the industrialized world are most likely to suffer from. They also have an incredibly active lifestyle, getting more physical activity in a typical day than most Americans get in a week.

My work with the Hadza showed that, surprisingly, even though they are so physically active, Hadza men and women burn the same number of calories each day as men and women in the US and other industrialized countries. Instead of increasing the calories burned per day, the Hadza physical activity was changing the way they spend their calories—more on activity, less on other, unseen tasks in the body.

The takeaway for us here in the industrialized world is that we need to stay active to stay healthy, but we can’t count on exercise to increase our daily calorie burn. Our bodies adjust, keeping energy expenditure in a narrow range regardless of lifestyle. And that means that we need to focus on diet and the calories we consume in order to manage our weight. At the end of the day, our weight is a matter of calories eaten versus calories burned—and it’s really hard to change the calories we burn! …


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


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.

As the article makes clear, there’s still lots of good reason to exercise even if it won’t help you much to lose weight.  But, I really wish some extra exercise meant that extra donut was okay– but it probably doesn’t :-(.  Also, I’m still pretty curious how this balances out at more typical levels.  E.g., If my typical day included moderate exercise and 2500 calories burned, does an atypical day where exercise substantially more than normal yield me no calorie out benefit?  

About Steve Greene
Professor of Political Science at NC State

4 Responses to Calories IN. Calories out.

  1. Damon Circosta says:

    But donuts taste so good

    Dictated to Siri. Typos are her fault


  2. itchy says:

    I still buy the “calories in, calories out” philosophy, but maybe it’s more like:

    calories out

  3. Jim Danielson says:

    I’ve tried thinking harder to burn more calories but it doesn’t seem to be working.

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