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Of course, the mere suggestion that the Atkins diet and others like it are worthy of scientific attention still makes many experts bristle. Yet it is also clear that the low-fat paradigm has developed some cracks in its facade. It turns out that not all fats are bad for you. Those found in fish, nuts and certain vegetables may actually increase your chances of living a good long life. By the same token, not all diets that are low in fat are necessarily healthy--as anyone who has ever truly considered the difference between a low-fat banana cream pie and a banana could tell you.
About one thing, however, there is no dispute. As a society we are clearly in a state of nutritional crisis and in need of radical remedies. The statistics are sobering. After 30 years of seemingly solid advice aimed at lowering dietary fat, Americans have grown collectively fatter than ever. Today more than 60% of adults in the U.S. are classified as overweight or obese. So many children have become so heavy that pediatricians are now facing an epidemic of Type 2 diabetes and hypertension--diseases that are closely associated with overweight and that were unheard of among youngsters just a generation ago.
The change has been so swift and so pervasive that no simple explanation is possible. Maybe we didn't understand all the ramifications when we jumped on the low-fat bandwagon. We also failed to factor in suburban sprawl and six-lane expressways, school cafeterias and fast-food chains, movie theaters and television, advertisers and food processors. "We live in a toxic environment," says Kelly Brownell, director of the Yale University Center for Eating and Weight Disorders. "Physical activities have been engineered out of day-to-day life, and the food environment grows worse by the day. We took Joe Camel off the billboards, but we celebrate Ronald McDonald."
On one level, there is no mystery about why we as a society are fat. We are fat because we consume too many calories and expend too few. Though it is true that the proportion of fat in our diet has fallen from 40% in 1990 to roughly 34% today, the calories available in the food we consume have gone up, from 3,100 calories per capita per day in the 1960s to 3,700 in the 1990s, according to the U.S. Department of Agriculture (USDA). "And that alone," says New York University nutritionist Marion Nestle, "is sufficient to explain the obesity epidemic."
But there is a deeper question--one that has plagued anyone who has ever struggled to take off more than a few pounds. And that is: How do some folks manage to live in the same "toxic environment" and never gain weight? Indeed, the question of why so many of us are fat is just half the puzzle. "You can just as easily flip it around," says Jeffrey Friedman, a molecular geneticist at Rockefeller University, "and ask why--despite equal access to calories--is anyone thin?"
The quest to answer this double-sided question is in its earliest stages. Already, however, a series of fascinating insights into the biology of obesity has emerged. Behind our broadening behinds and widening waistlines, scientists say, lies a complex array of genes that, directly and indirectly, links our gut to our brain. These genes, honed by millions of years of evolution, appear to have betrayed many of us in the 21st century world.