WASHINGTON -- Put down that cheeseburger and listen up: If food has become what sex was a generation ago -- the intimidatingly intelligent Mary Eberstadt says it has -- then a cheeseburger is akin to adultery, or worse. As eating has become highly charged with moral judgments, sex has become notably less so, and Eberstadt, a fellow at Stanford University's Hoover Institution, thinks these trends involving two primal appetites are related.

In a Policy Review essay "Is Food the New Sex?" -- it has a section titled "Broccoli, pornography, and Kant" -- she notes that for the first time ever, most people in advanced nations "are more or less free to have all the sex and food they want." One might think, she says, either that food and sex would both be pursued with an ardor heedless of consequences, or that both would be subjected to analogous codes constraining consumption. The opposite has happened -- mindful eating and mindless sex.

Imagine, says Eberstadt, a 30-year-old Betty in 1958, and her 30-year-old granddaughter Jennifer today. Betty's kitchen is replete with things -- red meat, dairy products, refined sugars, etc. -- that nutritionists now instruct us to minimize. She serves meat from her freezer, accompanied by this and that from jars. If she serves anything "fresh," it would be a potato. If she thinks about food, she thinks only about what she enjoys, not what she, and everyone else, ought to eat.

Jennifer pays close attention to food, about which she has strong opinions. She eats neither red meat nor endangered fish, buys "organic" meat and produce, fresh fruits and vegetables, and has only ice in her freezer. These choices are, for her, matters of right and wrong. Regarding food, writes Eberstadt, Jennifer exemplifies Immanuel Kant's Categorical Imperative: She acts according to rules she thinks are universally valid and should be universally embraced.

Betty would be baffled by draping moral abstractions over food, a mere matter of personal taste. Regarding sex, however, she had her Categorical Imperative -- the 1950s' encompassing sexual ethic that proscribed almost all sex outside of marriage. Jennifer is a Whole Foods Woman, an apostle of thoroughly thought-out eating. She bristles with judgments -- moral as well as nutritional -- about eating, but is essentially laissez-faire about sex.

In 50 years, Eberstadt writes, for many people "the moral poles of sex and food have been reversed." Today, there is, concerning food, "a level of metaphysical attentiveness" previously invested in sex; there are more "schismatic differences" about food than about (other) religions.

If food is the new sex, Eberstadt asks, "where does that leave sex?" She says it leaves much of sex dumbed-down -- junk sex akin to junk food. It also leaves sexual attitudes poised for a reversal. Since Betty's era, abundant research has demonstrated that diet can have potent effects, beneficial or injurious. Now, says Eberstadt, an empirical record is being assembled about the societal costs of laissez-faire sex.

Eberstadt says two generations of "social science replete with studies, surveys and regression analyses galore" have produced clear findings: "The sexual revolution -- meaning the widespread extension of sex outside of marriage and frequently outside commitment of any kind -- has had negative effects on many people, chiefly the most vulnerable; and it has also had clear financial costs to society at large."

In 1965, the Moynihan Report sounded an alarm about 23.6 percent of African-American children born out of wedlock. Today the figure for the entire American population is 38.5 percent, and 70.7 percent for African-Americans. To that, add AIDS and other sexually transmitted diseases, and the unquantifiable coarsening of the culture and devaluing of personal intimacy.

Today "the all-you-can-eat buffet" is stigmatized and the "sexual smorgasbord" is not. Eberstadt's surmise about a society "puritanical about food, and licentious about sex" is this: "The rules being drawn around food receive some force from the fact that people are uncomfortable with how far the sexual revolution has gone -- and not knowing what to do about it, they turn for increasing consolation to mining morality out of what they eat."

Perhaps. Stigmas are compasses, pointing toward society's sense of its prerequisites for self-protection. Furthermore, as increasing numbers of people are led to a materialist understanding of life -- who say not that "I have a body" but that "I am a body" -- society becomes more obsessive about the body's maintenance. Alas, expiration is written into the leases we have on our bodies, so bon appetit.