I've been on a diet for 17 weeks, though it feels like it began early in the Carter administration.

It was my Washington Post colleague E.J. Dionne who provided the inspiration and the method. When I asked the secret of his weight loss, he told me: "Two things: Cutting carbohydrates and a bout of the stomach flu."

I took the low-carb route.

The sameness of healthy eating has begun gnawing at me. I never want to see a lean protein again -- though this, apparently, is the only sort allowed for the rest of my life.

Vegetables once crisp and colorful now seem raw and garish. Healthy probiotics have all the appeal of parasites. Then again, I miss bread and pasta less than I thought I would, which would have been crazy talk to my Italian ancestors.

My only real craving has been peanut butter, which I have sometimes sought out nocturnally with the biologically driven imperative of a migrating goose. Dieting is a reintroduction to the mind-body problem -- a reminder that our pilgrim souls are fastened to a peanut butter-craving animal.

During a diet, or in a hospital bed, the mind pays tribute to its cranky, demanding host.

I have generally avoided the latest dieting technologies. Recent studies had found that people using large forks eat less.

Dining in front of a mirror shames people into reducing their consumption by about a third. The color blue in the dining area seems to be an appetite suppressant.

But this image -- eating with an oversized implement, while staring at your own shrinking image, surrounded by a sea of bright blue -- seems less like a dieting strategy than the outcome of ingesting hallucinogenic mushrooms, which are also low-carb.

It is easy to blame yourself for the scale your self assumes. My research however, indicates that I am the victim of complex historical forces.

The human genome was honed for hunter-gatherers -- tireless, long-distance trackers of game, capable of storing energy in fat during long winters and frequent famine. Feed a hunter-gatherer 150 to 170 pounds of sugar a year and place him in front of a television set for 4.8 hours a day, and you get the average American.

A job hunched in front of a computer screen, I can attest, is also not particularly good preparation for the hunt. Vast civilizational trends have left many of us with 20 or 30 pounds of unsightly historical epiphenomenon.

As Karl Marx would remind us, even impersonal forces produce flesh-and-blood villains. The second-largest employer in America (following government) is the food-service industry, packing calories, salt and fat into ever-larger servings, marketed to ever-larger children.

Government adds to the buffet by subsidizing the growth of nutritionally empty grains such as corn, used to make sweeteners and to fatten the means of hamburger production.

Progressive city councils have begun taking on the culinary-political complex. San Francisco's board of supervisors voted to ban McDonald's Happy Meals as the equivalent of cigarette advertising to children.

"We're part of a movement," said Supervisor Eric Mar, "that is moving forward an agenda of food justice." Denmark recently imposed the first "fat tax" on unhealthy foods.

Not being a progressive, I find the desire to politicize every social problem to be problematic. Not being a libertarian, I could be persuaded of the usefulness of public efforts to discourage high levels of sugar and salt intake, which impose a private and public cost.

But what interests me most is my own growing censoriousness as I've shed a few pounds. I had not realized that diets, along with producing feelings of lightheadedness, also result in feelings of moral superiority.

Having foresworn McDonald's and Dairy Queen, I find myself pitying those poor souls still addicted to Big Macs and Blizzards. Judgmentalism comes unbidden -- as strong as in San Francisco or Denmark. A Snickers bar now seems such a shoddy little sin -- the nutritional equivalent of cigarettes and porn.

So a diet is also a lesson in moral philosophy. It is distressingly easy to condemn others for failings I shared a few months ago -- and could share again with one ill-advised trip to the 7-Eleven.

Perhaps it is for the best that most weight-control plans eventually fail. There is no Pharisee like a Pharisee on a diet.