BECAUSE we all needed yet another set of rules to follow, because we had not yet been sufficiently bombarded with dictates about the colors of the fruits and vegetables we should eat and the ideal intake of alcohol and the optimal frequency of low-impact exercise, the Journal of the American Medical Association came along last week to tell us that serious calorie restriction might best serve the quest for a long, disease-free life.

The number of calories in the daily diets of some participants in this latest study was -- gulp -- 890. Which, by my nonscientific research, is less than the average teenage or adult American who lives within a half mile of a Burger King and has not had gastric bypass surgery consumes for dinner. That might be considered a helpful target, except that it's so ludicrously unattainable, in professions other than modeling and zip codes other than 90210, that there isn't anything helpful about it.

It's also hard to see the point of it. If living to 99 means forever cutting the porterhouse into eighths, swearing off the baked potato and putting the martini shaker into storage, then 85 sounds a whole lot better, and I'd ratchet that down to 79 to hold onto the Häagen-Dazs, along with a few shreds of spontaneity. It's a matter of priorities.

Do we really want as many years as we can get, no matter how we get them? At what point does the pursuit of an extended life -- a pursuit that pivots on the debatable assumption that habit can outwit heredity, not to mention chance-- become the entire business of a life? Is longevity all it's cracked up to be?