JOHN TIERNEY writes amusingly in his column today about the new JAMA study on weight and mortality.

For those of us lacking six-pack abs, this week's report that the overweight live longer is the greatest medical news in history. The authors of this study deserve a Nobel, not just for medicine, but for peace, too.

They have taken away the favorite cudgel of the scolds who used the "obesity epidemic" as an excuse to attack the flabby. The supposedly deadly consequences of fat provided the scientific rationale for the last politically correct form of prejudice.

The fatophobes are fighting on, disputing the new study and arguing that it still shows the fatal dangers of being seriously obese. But they have lost the scientific high ground. Not only do people of "normal" weight die younger than the moderately overweight, the study shows, but thin people die even younger than those of normal weight.

The Center for Consumer Freedom says the moral of the JAMA study is that "fitness (not fatness) is key" to longevity. And in case you're wondering about the credentials of the people who say this, don't worry. They are stellar.

Taking a direct stab at previous research that overemphasizes people's waist lines, the JAMA article notes that "most studies" of the flawed Body Mass Index (BMI) standard "and other measures of obesity have not adequately accounted for physical fitness." Says who? The authors hail from the National Institutes of Health, the University of Florida College of Medicine, the University of Pittsburgh Medical Center, the Rhode Island Hospital, the Atlanta Cardiovascular Research Institute, and the Cedars-Sinai Medical Center.

David Brooks, snarky as ever, makes an attempt at conveying good cheer at the news that fat is healthier than skinny, but his real reason for crowing is that, according to him, the study proves that there is no point in being disciplined and responsible, because life rewards irresponsibility and slovenliness.

Mostly, I'm happy on an existential level. I like to be reminded that the universe is basically crooked. This is what the zero-tolerance brigades and all the better living gurus never quite get. They're busy trying to mold everybody into lifelong valedictorians, who spend their adulthood as carb counters and responsible flossers - the sort of organized folk who actually read legal documents before they sign them.

In reality, life is perverse and human beings don't get what they deserve. The people with the worst grades start the most successful businesses. The shallowest people end up blissfully happy and they are so vapid they don't even realize how vapid they are because vapidity is the only trait that comes with its own impermeable obliviousness system. The people regarded as lightweights, like F.D.R., J.F.K. and Ronald Reagan, make the best presidents, while you - so much more thoughtful and better read - would be a complete disaster.

Life isn't fair, logic is of limited value and, as Woody Allen observed years ago, everything your parents once thought was good for you turns out to be bad for you: sun, milk, red meat and college.

The chief moral lesson I take away from this report is that Mother Nature is happy to tolerate marginally irresponsible misbehavior. She doesn't want you to go completely to seed. If you're truly obese and arouse hippos when you visit the zoo, you could still punch your ticket at any moment.

Naturally, being David Brooks, he does not get it at all. The "chief lesson" in this study is that morality and weight have nothing to do with each other -- but if Brooks insists on bringing "personal responsibility" into this issue, then it must be the thin people who count calories obsessively but never get any exercise who are being irresponsible; and the overweight people who eat what they want to eat but are physically active are the ones who are behaving appropriately.