Washington ? As one who prefers “comfortable fit” khakis to the other kind, I hesitate to weigh in — as it were — on obesity. But between the surgeon general’s 1991 report on the subject and last year’s stop-me-before-I-supersize lawsuits against McDonald’s, the issue is clearly gaining traction.

As usual, it’s about the children. There is much concern expressed in the media about the sedentary habits of modern American adolescents. I gather that they tend to munch on snacks, play computer games and watch TV for hours on end instead of leading the austere, scholarly, muscular-Christian lives of my generation. When we Baby Boomers weren’t translating Ovid for pleasure, or sweating away the hours on the baseball diamond or tennis court, we were sawing away on the cello, or helping Father gather firewood for the winter. What a contrast to today’s hedonistic youth!

The truth, of course, lies somewhere in the middle. Anyone walking down a city street is aware that many Americans are heftier than they should be, and some of these are decidedly obese. Yet these anecdotal emblems are symbols of social success, not failure: Whereas a century ago the rich were fat and the poor were thin, the opposite appears to be the case today. We are, paradoxically, capable of feeding our least fortunate citizens to excess while promoting an obsessive culture of fitness. Only in America do anorexia and obesity unhappily co-exist.

Still, there is evidence that American children are not as active as they should be: With the new sophistication and growth of the high school curriculum, there is less daily physical exercise than there used to be — in some instances, none at all. And with the decline of the much-reviled Ozzie-and-Harriet (or is it Ward-and-June-Cleaver?) household, the notion of a well-balanced family dinner has slowly given way to improvised meals, heavy on fats, sweets and carbohydrates, eaten on the run, or with undue haste. Many children seem better acquainted with the contents of the Wendy’s menu than the furniture in their family’s vestigial dining room.

These social tendencies of the past few decades reveal themselves in lamentable ways. The substitution of fast food or packaged meals for Mom’s home cooking has led to more volume and less nutrition: “Family restaurants” are more interested in satisfying your gluttony than making sure that you eat your broccoli, and the frozen-food aisles are stuffed with Hungry Man meals. A recent article in The Washington Post quantified the extent to which McDonald’s, for example, has significantly increased its portions: The relatively modest hamburger and French fries of 35 years ago are now the Quarter Pounder with Cheese and supersize fries, washed down with Chocolaty Chip cookies and a McFlurry.

Nor have the schools been much help. Because federally subsidized vegetables tend to disagree with juvenile palates, school cafeterias are a cardiologist’s nightmare: Soft drinks, salty snacks, ice cream, pasta, cheese and chips abound. This is not to say that healthy foods aren’t offered to students; it’s just that the kids aren’t compelled to eat wisely, and dangerous alternatives are readily available, often at discount prices to cash-strapped systems.

It’s a problem, to be sure, but is there a solution? Since school systems tend to respond to (a) pressure from constituents and (b) fiscal constraints, it is difficult to see them mandating healthy, adult-style habits for teen-agers eager to stuff themselves silly. Instead of reviling bureaucrats who offer pizza and Coke, it makes more sense to exhort parents to teach their children the ingredients of healthy living. This is not likely to yield spinach-craving adolescents, or lessen any 17-year-old’s fondness for snacks; but it would instill standards that, someday, might take root.

And it is altogether too easy to blame McDonald’s for luring us into the consumption of Big Macs. McDonald’s, like any merchant, is in the business of satisfying its customers, and hunger and affluence lead to bigger portions. The truth is that three-quarters of the meals Americans consume are eaten at home. And while grocery stores sell vegetables, whole grains and yogurt, they also stock cookies, chocolate sauce and peanuts. Is the grocer to be blamed for our judgment as consumers?

When we choose to dine out, there are not just inexhaustible varieties of restaurants, but dozens of choices on individual menus. The key to the issue is not blame, but responsibility, and personal responsibility for how we choose to live. There is no law compelling anyone to buy the biggest burger in the joint, or supersize the fries, or demand a jumbo soft drink, or sundae with nuts. There is such a thing as free will, even at McDonald’s, and the virtues of restraint and moderation remain intact.