Word association. Carbs. First thing that comes to mind. What is it? (Don’t worry, this is a safe place.)
Cutting carbs? Low-carb? Carbs are fattening? Then it’s time to forget everything you think you know about carbs.
First off, low-carb people are right: low-carb diets cause weight loss. It’s well established that low-carb diets work1,2—at least if “work” means “are usually at least marginally effective for short-term weight loss.” Still, given the anemic results of most weight-loss efforts, this is nothing to sneeze at. Low-carb diets are usually somewhat successful, sometimes smashingly so.
I grant all this; I’m no savage. But a certain appalling fallacy has crept out of these facts and slithered into millions of minds:
Cutting carbs causes weight loss. Thus, carbs are fattening.
This is patently false.
Where to begin.
Discounting alcohol (who can?), there are only three major calorie sources: fat, protein, and carbs. Protein is not primarily used for energy.3 That leaves only two major energy sources: fat and carbs. Both are absolutely ancient. Our evolutionary lineage has been eating carbs on a large scale for at least 60 million years.4
To our knowledge, though, this crippling epidemic of overweight and obesity is exclusively a very modern problem.
What’s the simplest way to prove that carbs are not inherently fattening? I guess it would be to find entire populations of free-living humans who gorge on carbs every day, are otherwise unexceptional, and aren’t the least bit fat—like, at all. So that’s what I did.
So we eat an awful lot of carbs. And we’re an awful lot of fat. Coincidence?
Ask the Kitavans. They’re a Melanesian people whose diet was 69% carbs7—mainly from tubers and fruit—when they were studied in the ’90s (an excellent decade). Unlike us, the Kitavans were extremely skinny—the average middle-aged Kitavan man and woman had BMIs of 20 of 18, respectively.8
To give these numbers context, despite my best efforts, I’m afraid most people would call me “skinny” rather than “muscular.” My BMI is 23.4 (“normal”). Despite being visibly thin (sigh), I’d have to lose 26 pounds to have a BMI of 20.
But were the Kitavans skinny-fat? Did their feathery weights belie closet, carb-fueled health problems? The evidence suggests a hard no. In Kitava, heart disease and stroke, for example, were virtually nonexistent.9
You really can’t explain the Kitavans away. They ate all the food they wanted. According to the lead scientist, in Kitava, “lack of food is an unknown concept.”10
Nor were they very active. They weren’t sedentary, but their average daily calorie expenditure (for you sticklers) was ~1.7x their basal metabolic rate—which is only “moderately active.”11 There are plenty of obese people more active than this.
So the Kitavans ate tons of carbs every day, weren’t terribly active, and were thin as rails.
And before you can say “genes,” there were two cases of abdominal obesity in Kitava (just two). Both bulging guts belonged to Kitavan men who were actually living abroad in urban settings at the time of the study (eating “modernly”), and were only back in Kitava on a visit.12
This suggests it’s the traditional Kitavan diet—not genes—that’s the secret sauce.
And they’re not alone.
Take the Hadza hunter-gatherers of Tanzania (that’s Africa, according to Google). Similar to the Kitavans, ~68% of the Hadza diet is carbs.13 And remarkably, about 50% of Hadza calories come directly from sugar—oh, the HUMANITY!—mainly via honey and fruit.
Talk about an atomic fructose bomb—every day, for life. Honey (almost pure sugar) makes up 15% of total Hadza calories—which is almost the exact same portion added sugars take up in the US diet (14.9%).14
And sugar, at least, is surely fattening.
Similar to the Kitavans, the average Hadza BMI is just over 20.15
While the Hadza walk an average of four to seven miles a day—far more than the typical Westerner—a fascinating 2012 study found that, adjusted for weight, Hadza people don’t actually burn more calories than the typical Western couch potato.16
How is this possible? While the Hadza burn more calories moving around (of course), it turns out we Western couch potatoes burn so many more calories at rest—again, adjusted for weight—that it all evens out. According to the scientists,
Hadza hunter-gatherers challenge the view that Western lifestyles result in abnormally low energy expenditure, and that decreased energy expenditure is a primary cause of obesity.17
We don’t have time to parse this bombshell now, but it supports the idea that the Hadza are so lean because of their diet, not in spite of it.
And now for my ace in the hole. Enter the Murapin people of Papa New Guinea. The Murapin were farmers and pig-herders studied in the ’60s and ’70s (great years, I’m told). This is not a misprint: the average Murapin diet was 94.6% carbs (mostly from sweet potatoes).18
This amount of carbs is almost sickening. The average Murapin man ate 543 grams of carbs a day—a year-round carbicide. If carbs are the least bit fattening, Murapins would have put the “morbid” in morbidly obese.
At ages 20-29, Murapin men weighed an average of 132 pounds, while women weighed 112 pounds—and unlike us, their weights declined with age.19 Heart disease was rare among the Murapins, and diabetes was nonexistent.20 And Murapin men ate an average of 2300 calories a day,21 so you can’t say they were starving or something (nice try, reader).
There you have it. Three populations that ate cartoon amounts of carbs, were thin as rails, and healthy as horses.
In fact, most epidemiological studies of “modern” people show that the more carbs we eat as a percentage of total calories, the lower our BMIs,22 and the lower our chances of being overweight or obese.23
There are confounding variables here; you can’t say eating lots of carbs makes people thin.
But you can say it doesn’t make people fat.
This is decisive proof that carbs aren’t inherently fattening—the sort of proof that burns a theory to the ground and then salts that ground so nothing can ever grow there again.
But it also reveals something deeper.
The Murapin weren’t eating “carbs,” they were eating sweet potatoes.
The Hadza weren’t eating “sugar,” they were eating fruit and honey.
The Kitavans weren’t eating “starch,” they were eating tubers.
Natural whole foods like these—the kind we’ve been eating and adapting to for millions of years—aren’t fattening.
If you look at a food’s back label, you shouldn’t worry about grams of fat or grams of carbs. Instead, you should worry about the ingredients list.
Fat and carbs don’t make us fat. It’s only processed fat (vegetable oil) and processed carbs (white flour and added sugar) in processed foods (foods with more than one ingredient) that inherently lead to overeating and weight gain.
More on that later. Next post I’ll go to bat for some stellar carbs—babies that got thrown out with the low-carb bathwater.
3. Frayn, Keith. Metabolic Regulation: A Human Perspective. Oxford: Wiley Blackwell, 2010 Kindle File, 7.3, Location 4399 of 9142.
4. Klein, Richard. The Human Career: Human Biological and Cultural Origins. Chicago: University of Chicago Press, 1999.
10. Lindeberg, Staffan. Food and Western Disease: Health and Nutrition from an Evolutionary Perspective. Hoboken: Wiley-Blackwell, 2010. Kindle File, Chapter 4.5, Location 3081.
11. Ibid., Chapter 4.1, Location 2319.
12. Ibid, Chapter 4.5, Location 3102.
18. Trowell, HC. and Burkitt, D.P. Western Diseases: Their Emergence and Prevention. Cambridge: Harvard University Press, 1981. Page 174.
19. Ibid., page 175.
20. Ibid., pages 180-181.
21. Ibid., page 174.