Boston ? This is probably as good a moment as any to rewrite the definition of Schadenfreude. It’s not just the pleasure derived from the misfortunes of others. It’s the pleasure derived from the misfortunes of others who are thinner than you are.

My shot at dictionary dissing comes from watching the joyful public reaction to the most recent and revisionist report on the dangers of being overweight. It turns out that those with an extra bit of padding actually have a lower risk of premature death than those without it. More to the (mischievous) point, the very thin have a greater risk than those designated normal.

The news from the Centers for Disease Control was greeted with the sort of public glee usually reserved by the collapse of a self-righteous fitness guru preferably while taping a public service ad on the health benefits of exercise. The headlines gloated “Pudgy is Good,” “Hot Fudge and Health” and “You Can Be Too Thin, After All.” The only thing that could have made people happier was a study proving you can also be too rich, but they’ll never get the funding out of this White House.

I am something of an expert on good/bad revolving medical news. The wine that was bad for breast cancer was good for heart disease. The hormones that eliminated the symptoms of menopause could also eliminate old age. That sort of thing.

But if there were a prize for yo-yo sciencing it would be in research on the “epidemic of obesity.” A year ago the same CDC warned that 400,000 Americans died prematurely every year from obesity. It ranked No. 2 on the grim reaper’s list of helpers right after smoking.

This has led to more dire warnings. The American Cancer Society added a “Great American Weigh-In” to its “Great American Smokeout.” Just last month, there was another study claiming that obesity was reducing life expectancy by up to nine months. The author called obesity a “massive tsunami heading toward the U.S.”

Meanwhile, we were hearing more from the eat-almost-nothing-and-live-forever crowd whose folk hero, inventor Ray Kurzweil, exists on nearly as many vitamin supplements as calories. And peer group pressure being what it is, this month the Cookie Monster was given an identity crisis and a nutritious breakfast of pears, cereal, toast and milk on Sesame Street.

However, it appears that rumors of death from obesity were exaggerated. It was a new statistical model rather than a new diet that brought the death toll due to obesity down from 400,000 to 112,000. At the same time, being overweight is preventing 86,000 extra deaths while being underweight is causing 34,000.

This has scientists of all sizes lining up their explanations. On one side are those who believe that extra weight is truly bad for you but medicine is getting better at treating it. They regard the overweight as if they were irresponsible drivers protected by seat belts.

On the other side are scientists who speculate that having more bulk may help you through the sick bed when you are older. They are the heroes of all those who dearly love the idea that living longer is the best revenge.

The government Web site has remained neutral on this life-or-death question. On mypyramid.gov, the folks who once labeled sugar a “food group” now have a newly restructured and deconstructed chart of 12 body types that does not include my-pear-a-mid.gov. Never mind.

I have no idea how long it will be before this Schadenfreude is overshadowed. After all, it’s notoriously hard to figure out the role of weight in mortality. Somewhere another batch of scientists is working on the next episode of “As the Research Turns.” But the reaction gives you a hint of how the public has turned.

“The Atkins Diet” has finally gone the way of Dr. Atkins. “The South Beach Diet” now coexists on the best-seller list with a Francophile diet. “French Women Don’t Get Fat,” carries 48 recipes and joie de vivre without a single “Sweet’N Low.”

So the CDC may have given us more than a chance to gloat that the women Tom Wolfe dubbed “X-Rays” are headed for X-rays and a moment to delight in the notion that the biggest body mass index may not be the biggest problem of the body politic.

Is it possible that we are headed to a marginally more sane approach to weight? Has the CDC with all its revisionists prodded us to a more cynical and yet cheerful relationship to food, health, the mirror and the dinner table?

Did I hear someone say “Fat chance”?