Please Do Not Feed the HumansThe global explosion of fat.

In 1894, Congress established Labor Day to honor those who "from rude nature have delved and carved all the grandeur we behold." In the century since, the grandeur of human achievement has multiplied. Over the past four decades, global population has doubled, but food output, driven by increases in productivity, has outpaced it. Poverty, infant mortality, and hunger are receding. For the first time in our planet's history, a species no longer lives at the mercy of scarcity. We have learned to feed ourselves.

We've learned so well, in fact, that we're getting fat. Not just the United States or Europe, but the whole world. Egyptian, Mexican, and South African women are now as fat as Americans. Far more Filipino adults are now overweight than underweight. In China, one in five adults is too heavy, and the rate of overweight in children is 28 times higher than it was two decades ago. In Thailand, Kuwait, and Tunisia, obesity, diabetes, and heart disease are soaring.

Hunger is far from conquered. But since 1990, the global rate of malnutrition has declined an average of 1.7 percent a year. Based on data from the World Health Organization and the U.N. Food and Agriculture Organization, for every two people who are malnourished, three are now overweight or obese. Among women, even in most African countries, overweight has surpassed underweight. The balance of peril is shifting.

Fat is no longer a rich man's disease. For middle- and high-income Americans, the obesity rate is 29 percent. For low-income Americans, it's 35 percent. Among middle- and high-income kids aged 15 to 17, the rate of overweight is 14 percent. Among low-income kids in the same age bracket, it's 23 percent. Globally, weight has tended to rise with income. But a study in Vancouver, Canada, published three months ago, found that preschoolers in "food-insecure" households were twice as likely as other kids to be overweight or obese. In Brazilian cities, the poor have become fatter than the rich.

Technologically, this is a triumph. In the early days of our species, even the rich starved. Barry Popkin, a nutritional epidemiologist at the University of North Carolina, divides history into several epochs. In the hunter-gatherer era, if we didn't find food, we died. In the agricultural era, if our crops perished, we died. In the industrial era, famine receded, but infectious diseases killed us. Now we've achieved such control over nature that we're dying not of starvation or infection, but of abundance. Nature isn't killing us. We're killing ourselves.

You don't have to go hungry anymore; we can fill you with fats and carbs more cheaply than ever. You don't have to chase your food; we can bring it to you. You don't have to cook it; we can deliver it ready-to-eat. You don't have to eat it before it spoils; we can pump it full of preservatives so it lasts forever. You don't even have to stop when you're full. We've got so much food to sell, we want you to keep eating.

What happened in America is happening everywhere, only faster. Fewer farmers' markets, more processed food. Fewer whole grains, more refined ones. More sweeteners, salt, and trans fats. Cheaper meat, more animal fat. Less cooking, more eating out. Bigger portions, more snacks.

Kentucky Fried Chicken and Pizza Hut are spreading across the planet. Coca-Cola is in more than 200 countries. Half of McDonald's business is overseas. In China, animal-fat intake has tripled in 20 years. By 2020, meat consumption in developing countries will grow by 106 million metric tons, outstripping growth in developed countries by a factor of more than five. Forty years ago, to afford a high-fat diet, your country needed a gross national product per capita of nearly $1,500. Now the price is half that. You no longer have to be rich to die a rich man's death.

Soon, it'll be a poor man's death. The rich have Whole Foods, gyms, and personal trainers. The poor have 7-Eleven, Popeye's, and streets unsafe for walking. When money's tight, you feed your kids at Wendy's and stock up on macaroni and cheese. At a lunch buffet, you do what your ancestors did: store all the fat you can.

That's the punch line: Technology has changed everything but us. We evolved to survive scarcity. We crave fat. We're quick to gain weight and slow to lose it. Double what you serve us, and we'll double what we eat. Thanks to technology, the deprivation that made these traits useful is gone. So is the link between flavors and nutrients. The modern food industry can sell you sweetness without fruit, salt without protein, creaminess without milk. We can fatten you and starve you at the same time.

And that's just the diet side of the equation. Before technology, adult men had to expend about 3,000 calories a day. Now they expend about 2,000. Look at the new Segway scooter. The original model relieved you of the need to walk, pedal, or balance. With the new one, you don't even have to turn the handlebars or start it manually. In theory, Segway is replacing the car. In practice, it's replacing the body.

In country after country, service jobs are replacing hard labor. The folks who field your customer service calls in Bangalore are sitting at desks. Nearly everyone in China has a television set. Remember when Chinese rode bikes? In the past six years, the number of cars there has grown from six million to 20 million. More than one in seven Chinese has a motorized vehicle, and households with such vehicles have an obesity rate 80 percent higher than their peers.

The answer to these trends is simple. We have to exercise more and change the food we eat, donate, and subsidize. Next year, for example, the U.S. Women, Infants, and Children program, which subsidizes groceries for impoverished youngsters, will begin to pay for fruits and vegetables. For 32 years, the program has fed toddlers eggs and cheese but not one vegetable. And we wonder why poor kids are fat.

The hard part is changing our mentality. We have a distorted body image. We're so used to not having enough, as a species, that we can't believe the problem is too much. From China to Africa to Latin America, people are trying to fatten their kids. I just got back from a vacation with my Jewish mother and Jewish mother-in-law. They told me I need to eat more.

The other thing blinding us is liberal guilt. We're so caught up in the idea of giving that we can't see the importance of changing behavior rather than filling bellies. We know better than to feed buttered popcorn to zoo animals, yet we send it to a food bank and call ourselves humanitarians. Maybe we should ask what our fellow humans actually need.