On January 20, 2003, the English journalist William Leith decides he has to lose weight. That’s the day he gets on the bathroom scale and finds that it’s “the fattest day of my life”: he’s just over six feet tall and he weighs two hundred and thirty-six pounds. He feels lousy. He feels repulsive. In fact, he is repulsive. His girlfriend tells him to stop tucking his shirt into his trousers—“It just bulks you out”—and she doesn’t want to have sex with him anymore. He resolves, not for the first time, to do something about it. He gets on a plane and goes to New York to see Dr. Atkins, and he decides, more or less at the same time, to write a book about his eating problems. “The Hungry Years: Confessions of a Food Addict” (Gotham; $25) is the result: Bridget Jones with a Y chromosome, a significant coke habit, and a sneaky sort of intellectual ambition.

Leith’s book is about food addiction, but he’s interested in all sorts of addictions and what it is about our culture that makes it so easy to stuff ourselves, leaving us filled but unfulfilled: “This is the fat society. This is where people come, so they can have exactly what they want. And what they want is . . . more.” Most of all, he’s interested in himself. If he can figure out why he’s a food addict, then maybe he can figure out why he’s unhappy: “I am fat because I have other, deeper problems.” And if he can figure out what these deeper problems are then maybe he can stop stuffing himself. The cure has two courses. The physical bit is getting the weight off; the psychological bit is getting the weight off his mind. Dr. Atkins takes care of the first. Leith arrives at Atkins’s Manhattan clinic just months before the great man’s death, and about two years before the “low-carb craze” will itself be pronounced dead, with the venture-capital-crammed Atkins Nutritional, Inc., going into bankruptcy. But Atkins is then enjoying a boom: some months before, Gary Taubes published a pro-Atkins polemic in the Times Magazine (“What If It’s All Been a Big, Fat Lie?”), and a copy of New York that Leith picks up declares, “Welcome to a City in the Throes of CARB PANIC.” Leith masters the Atkins metabolic mantra: carbohydrates cause a rush of insulin; the insulin reduces blood glucose, causing cravings for more carbs; the body becomes insulin-resistant; and it shifts its attention to saving fat. Food fat doesn’t make your body fat; carbs are the culprit. As the pounds fall off—thirty in four months—Leith becomes an evangelist: his obituary of Atkins in the Guardian of April 19, 2003, is a panegyric. He reads Thomas Kuhn’s historical theory of scientific development and decides that Atkins is achieving nothing less than a dietary “paradigm change.” Atkins is a hero of our time.

The other part of the cure is psychotherapy. The Atkins diet is the instrumental arm of a psychodynamic search: it’s good to lose weight in the most effective way you can, but Leith still feels the need to sort out the psychic reasons that he’s become a fatty. There’s much recollecting of childhood traumas; original sin for Leith was not an apple but an apple pie—one of his grandmother’s that he secretly gobbled down at the age of seven. By the end of his therapy, Leith has concluded that there are “many many reasons” for his food addiction. It’s too complex for him to understand and, perhaps, too complex for any specific diet to remedy or therapy to analyze. As the Atkins diet works its wonders, he feels happier: he gets fit, and he even goes for a twenty-five-mile hike with his (new?) girlfriend, at the end of which they pop into a pub and tuck in like ordinary human beings—“spaghetti with a meat sauce, and some garlic bread, and a bottle of wine.” He’s genuinely hungry for the first time in ages. As the proverb has it, hunger turns out to be the best sauce. He winds up—like the growing number of Atkins dieters who have fallen away from the faith—edgily wondering if moderation in all things might, after all, be the answer.

Leith wants to lose weight because he wants not to be repulsive, and he’s not alone. A fifth of American men and more than a third of American women say they would like to lose at least twenty pounds, and you don’t need a statistical survey to establish that sexual appeal is a big part of the reason. Thundering denunciations of the equation between female thinness and sexiness have little effect. The world is unfair that way—possibly almost as unfair to fat men as to fat women. In Paddy Chayefsky’s 1955 play “Marty,” the title character whines, “I’m just a fat little man. A fat ugly man.” Moreover, statistics do establish that fat people earn less: possibly because the sort of people who make less money tend to be fat, possibly because fat people are discriminated against, or, most likely, a bit of both.

It was not always so. When the Duchess of Windsor pronounced that “you can never be too rich or too thin,” it was a sign of a demographic shift with far-reaching cultural consequences. The language that our ancestors used to assess people’s weight generally had a qualitative and whole-body character: “thin,” “gaunt,” “lean,” “lanky,” “stout,” “fleshy,” “corpulent,” “beefy,” “plump,” “portly,” and, finally, “fat.” With some exceptions, it was good to be fat: in the Oxford English Dictionary, one definition of the adjective is “in well-fed condition, plump,” and in its figurative usages it signalled an abundance of good things—“the fat of the land,” a “fat living” for a cleric. In 1825, the French gourmand Brillat-Savarin wrote that “to acquire a perfect degree of plumpness . . . is the life study of every woman in the world.” Male or female, body fat showed you were a considerable person, that you commanded resources. Holbein’s great portrait of Henry VIII depicts not an obese man but a Big Man. And fat John Falstaff was, in his own estimation, “a goodly portly man, i’faith, and a corpulent, of a cheerful look, a pleasing eye, and a most noble carriage.” In societies marked by dietary scarcity—which is to say in practically any period before the twentieth century and in practically any present-day country outside the developed world—bodily bulk functions as a visible mark of power, affluence, and even good humor. In the late Middle Ages, the starving masses fantasized about the Land of Cockaigne, where you could idly gorge yourself on cakes and cream, and the American hobo anthem “Big Rock Candy Mountain” was a version of the same never-satisfied dream of abundance: “There’s a lake of stew / And of whiskey too / And you can paddle / All around it in a big canoe.” It’s hard to avoid the conclusion that fat became ugly when the poor became fat.

But being fat isn’t just an aesthetic bane; it’s understood to be a medical one as well. And this, too, is a historically recent development. When Prince Hal dismissed Falstaff by telling him that “the grave doth gape for thee thrice wider than for other men,” he meant to make a joke, not to offer a summary of epidemiological evidence. Writers from the Renaissance through the nineteenth century were, of course, aware that health risks might attend the very fat. Even Brillat-Savarin, for whom obesity was essentially a moral, mechanical, and social problem, not a medical one, noted that extreme obesity “opens the way for various diseases, such as apoplexy, dropsy, and ulcers of the legs, and makes all other ailments more difficult to cure.” Yet our ancestors certainly did not recognize a linear relation between increasing weight and health risk, and an over-all association between the gluttonously fat and a shortened life span was sometimes even denied, as when Francis Bacon judged that “the greatest gluttons are often found the most long-lived.” Whatever objections the early moderns had to corpulence were as much moral as they were strictly medical. People who gorged themselves gave a visible sign of poor self-control; what mattered was their flawed character, not their mortality risk. Gluttony was a vice before obesity was a disease.