Boomers may never know if the most tantalizing avenues of anti-aging research will extend their lives: A trial on a drug's longevity effects would take at least a century to complete. The FDA is also unlikely to sanction a study that aims to forestall aging -- because aging, technically, is not a disease.

We're more likely to get a drug that prevents age-related diseases -- in other words, something that should improve our health span. The most promising avenues:

What is it? A diet high in nutrients, but very low in calories (about 30-40 percent lower than a maintenance level of calories, meaning the level at which you neither gain nor lose weight; the object is to slow metabolism, which is thought to lessen free radical production and improve glucose efficiency).

Evidence: Calorie restriction (CR) is by far the most studied anti-aging method. Trials involving lab rats and mice show those on CR diets have a slower decline in muscle function and immune response -- and they live up to 40 percent longer than regularly fed rodents. Monkeys also thrive on CR; they have lower body temperatures, lower blood-insulin levels, and a slower-than-usual decline of DHEA, a steroid hormone that normally decreases with age in both monkeys and humans.

Crew members from the Biosphere experiment of the '90s involuntarily practiced CR when food became scarce; after nearly two years, they emerged emaciated, but also with considerably lower blood sugar, blood pressure, and cholesterol.

Current or future use: Some people are already trying CR (the Calorie Restriction Society says it has 900 members worldwide). But most of us would find it too depriving, as it leads to weakness, feeling cold, and a loss of sex drive. The most likely use: figuring out how CR works, and manipulating genes to mimic its beneficial effects on cell metabolism, without having to undergo drastic dietary changes.

What is it? A growing body of evidence suggests that inflammation may be the driving force behind a wide variety of age-related diseases, including arthritis, heart disease, autoimmune disorders, and cancer. Many over-the-counter drugs combat inflammation (hence their name, nonsteroidal anti-inflammatory drugs; NSAIDs include aspirin, ibuprofen, and naproxen). Widely prescribed are statins (such as Lipitor and Pravachol), cholesterol-lowering drugs that also combat arterial inflammation.

Evidence: Older people tend to have more fat, and fat tissue produces pro-inflammatory molecules, which may partly explain why obesity is a major risk factor for age-related diseases and why CR appears to be effective in prolonging healthy life. Studies on long-term users of aspirin and other NSAIDs (such as heart-disease and arthritis patients) have demonstrated a reduced risk of heart attacks, colon cancer, and lung, prostate, and breast cancers. Preliminary studies on heart patients who take statins indicate they have a lower risk of Alzheimer's, diabetes, stroke, and possibly cancer and depression.

Existing and future use: Regular use of NSAIDs may cause serious gastrointestinal bleeding, so many experts feel the anti-aging benefits are not proven enough to justify the risk for healthy people. Current studies of patients who take statins should yield more information, but results are likely years away.