The World Is Fat

Science, technology, and life.
Nov. 30 2008 8:59 AM

The World Is Fat

Did you stuff yourself at Thanksgiving? Do you feel stupid about it? Do you wonder what the hell you were thinking as you went for that second helping of pie, your belly already swollen with turkey and cranberry sauce?

I'll tell you what you were thinking: the same thing your ancestors thought. They were suckers for fat, sweets, and extra helpings, too. The difference is, back in their day, those urges were healthy. You're not weaker or more gluttonous than they were. You just live in a different world—a world of cars, McDonald's, and corn syrup.

William Saletan William Saletan

Will Saletan writes about politics, science, technology, and other stuff for Slate. He’s the author of Bearing Right.


If you want to understand this mismatch between your genetically inherited tastes and your industrially inherited world, go pick up a copy of Barry Popkin's new book, The World Is Fat . (The title is a play on Tom Friedman's The World Is Flat .) I've written about Popkin before . He's an astute analyst of what's causing the obesity epidemic.

If you're like me, you grew up worrying about people starving in other countries. Your mom would tell you things like, "Eat your food. There are kids going hungry tonight." But hunger, as a global threat, is now dwarfed by overweight. According to Popkin, the population of obese and overweight people worldwide—1.6 billion—is now twice as large as the population of malnourished people.

This isn't the first time dietary changes have radically reshaped the human body. Popkin reports that average height shrank by about 4 inches during the Agricultural Revolution, apparently because previously diverse diets narrowed to a few crops. Then, as diets diversified again during the Industrial Revolution, average height in Europe and the United States regained 2 to 4 inches.

But Popkin's most important insight is that today's reshaping of our species—getting fat—is a result not of bad habits but of good habits that lost their context. During our ancestors' evolution, he explains,

To help us survive as a species, we developed preferences for sweet and fatty foods. ... Sweet foods provided nutritional balance to our diet, and they helped us survive during periods when animal foods were scarce. Sweet foods also provided the glucose needed to fuel our brains. At this time, however, sugars were only found in fruit. Because there are nine calories of energy in each gram of fat ... consuming as much fat as possible would have helped our hunter-gatherer and hominid ancestors to get an adequate amount of calories.

So, when you reach for that second helping of pie, you're doing what nature intended but in a world so radically transformed that nature's previous dictates no longer make sense. You're experiencing the disjunction between the rapid pace of technology and culture on the one hand and the slow pace of evolution on the other. Your body hasn't caught up to your world.

I'm a big fan of Popkin's theory for two reasons. First, it's consistent with the evidence. And, second, it's consistent with Human Nature's first law : Bad things happen because, initially, they're good. So, check out Popkin's book. Or if you're still not sold, start with a short overview of his argument. Bon app é tit!


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