She is the standard by which human life span is measured, an example, with other centenarians, of why medical researchers are confident they will find the key to life extension, maybe in this century. "I've been forgotten by a good God" was the way Calment described her longevity. Now, America's 77 million baby boomers are approaching their golden years, hopeful that they will be forgotten in the same manner. To echo a slogan from their youth, boomers seem to be saying, "Hell no, we won't go." Or, as comedian Woody Allen once said, "I don't want to achieve immortality through my work. I want to achieve it through not dying."

The human race's most fanciful whim is the quest to live forever. Deep thinkers expounded on the subject in ancient Egypt. White tea was the elixir of choice for Chinese emperors. Juan Ponce de Leon set sail for the New World to find the Fountain of Youth, and some 18th-century European men believed that goat-testicle implants would lengthen life and restore male libido to youthful levels. But "now, there are real medical possibilities of making inroads to the aging process," said Steven Austad, a gerontologist from the University of Idaho who is doing research on aging at the University of Texas Health Science Center at San Antonio.

Medical experts may debate how long it will take, but researchers are closer to unlocking the door to life extension than ever before in human history. "With genetic intervention, expect to see many more people -- half the population -- with life expectancy to 100," said Dan Perry, executive director of the Alliance for Aging Research in Washington, D.C. Given the track record of medical science, extending life is probably a matter of when, not if, said Dr. Donald Louria, a futurist who teaches at the University of Medicine and Dentistry of New Jersey.

"It would be foolish not to say that this science is moving incredibly fast and is likely to work in humans," Louria said. "If you look at studies in test tubes, with yeast, flies, worms, mice and rats and now monkeys, and see it moving up the scale, tell me this science won't be applied to people." The debate, among medical experts and demographers, is how much past 100 human life can go. "Can it be uncapped?" asked H.R. "Rick" Moody of the International Longevity Center-USA. "Some people say it can be 130 or 150 years. There are accounts of prophets living to 900. But it's not like calculating the speed of light. There's no definitive knowledge." Nonetheless, by the year 2100, Jeanne Louise Calment may no longer be in the Guinness book.

But don't get your hopes too high. Progress probably isn't being made fast enough to benefit baby boomers, the generation born between 1946 and '64, or even their children. Louria, among others who study aging, said there are formidable hurdles to clear. Laboratory life-extension studies on insects and rodents, for example, show side effects such as dwarfism and sterility. "We have no way of knowing whether longevity research will pan out," Moody said. "It's a delicate dance." Tom Perls, director of the New England Centenarian Study at Boston University, added, "People are so quick in a day of scientific miracles to jump from the petri dish to therapeutic application. "I'm not saying I'm a pessimist. Science is doing incredible things and making a lot of headway in understanding the aging puzzle. But will it increase the life span in my time? "Probably not," said Perls, who is 45.

New youth movement

The youth movement in America has nothing to do with young people. It revolves around baby boomers not entirely comfortable with the concept of growing old. "The quest for immortality has been an undercurrent forever, but it's now probably becoming a nakedly open desire," Austad said. Efforts to slow or turn back the biological clock resonate even more during a time of year when New Year's resolutions have not yet been forgotten, and when fitness trainers' schedules are as full as a homecoming queen's date book. Myriad studies counsel Americans about what to eat and drink, and what to avoid, to reduce the chances of life-shortening illnesses such as cancer, diabetes or heart disease.

TV, radio, print and Internet ads beckon consumers with supposed anti-aging remedies from prescription drugs such as human growth hormone to dietary supplements, often consumed like candy. The cosmetic-surgery business is booming, botox injections are de rigueur, and anti-wrinkle and renewal creams crowd pharmacy and supermarket shelves, suggesting that we can all look like Dorian Gray, even if we can't add a day to our lives.  And TV fitness gurus tout the benefits of exercise, promising washboard abs and sculpted bodies. In that context, the quest for eternal youth may not seem so far-fetched, especially given the groundbreaking medical advances of the past 100 years, which are sometimes taken for granted.

As recently as 1900, the average life expectancy in the United States was 47 years. Nowadays, people in their 40s suffer through midlife crises. A reduction in infant mortality, the eradication of diseases such as smallpox with vaccines and the introduction of antibiotics had a dramatic effect on life expectancy in the first half of the 20th century. Improved diagnostic tools, surgical procedures such as heart bypasses, organ transplants and arthroscopies, and the development of human regenerative medicine and replacement parts (hip and knee) every year give thousands of Americans a new lease on life. Life expectancy has increased to an average of 77 years, with women outliving men by an average of almost six years. The result is that the Earth is getting gray around the temples, with life expectancy edging closer to what futurist Joseph Coates calls the "biological set point" for the human species. You might call it the finish line. It's about 86 for men, 89 for women, Perls said.

Those who live to their middle to late 80s today generally have what is called "compressed morbidity," gerontologists say. They lead healthier lives, and their decline is usually swift because they avoid chronic illness. "Compression of morbidity means getting to 90 and dropping dead instead of getting to 80 and being impaired for 10 years," said Dr. Craig Rubin, who specializes in geriatrics research at University of Texas Southwestern Medical Center at Dallas. "We all age and slow down. But with the absence of disease, people will do fine," he said. Some cross the finish line and keep running, living into their 90s and beyond. But even with almost 80,000 centenarians in the world today, Perls said there is still only a 1-in-10,000 chance of reaching 100.  "The first thing that strikes me in centenarian studies is how incredibly rare and difficult it is to reach 100," he said. "It's like winning the lottery. You have to have the right combination of factors, and it's different for different people."

Caloric restriction

What will it take to improve the odds? Stem cell research appears to be the best bet right now. Stem cells are the source of all the blood cells in the body. They are found in bone marrow and regenerate indefinitely. They can be used as a repair kit for the body, replacing damaged and worn cells, thus helping fight diseases such as cancer and minimizing rejection in organ transplants. But the future, to use the buzz phrase in medicine, is "caloric reduction" or "caloric restriction." It is the key, gerontologists say, to life extension. Caloric restriction does not mean substituting a plain baked potato for french fries, eliminating dessert or eating smaller portions. Those are all positive steps in fighting obesity and reducing the risk of diabetes, some cancers and heart disease. This is more than cutting calories in the traditional sense. Caloric restriction makes the Weight Watchers diet look like a holiday feast. It means consuming a maximum of 700 calories a day. Every day. No exceptions. And they would have to be the right calories, too, supplying the necessary vitamins, minerals and nutrients. In laboratory experiments, caloric restriction has slowed the aging of rodents and extended their lives by up to three years. "It's one of the few cases where we have evidence that muscle function and immune function are preserved better," Austad said. That could add years if applicable to humans. But even if people had the motivation and discipline to eat like birds, they might not like what they see in the mirror. We'd look like walking skeletons. "People who eat 60 percent less would look horrible," Austad said. "They'd have no muscle, no testosterone, their bones would get premature osteoporosis." So researchers are working to find a way to simulate caloric restriction without cutting back on all the food. "We've gotten good keeping laboratory animals alive longer, some of them six times longer," Austad said. "By manipulating genetic pathways, flies, worms, mice all live longer. We're changing the genes of these animals." And someday, perhaps people, too, although it's too early to speculate when. "It will lead us to a pharmaceutical," Austad said. "The Fountain of Youth will be a pill."

False solutions

Medical advances like these take time, however, and Americans prefer quick fixes. That opens the door to opportunists -- including physicians -- who are profiting at the expense of consumers who will do anything to delay the inevitable. It's part of a multibillion-dollar scam, gerontologists say. The focus of their ire are so-called anti-aging medicines. Perls calls the marketing of these medicines "hype" and "quackery." The sellers give the public an inaccurate view of aging, he said. "It's a vicious, ugly depiction of older people in wheelchairs, staring at nursing home walls. "They scare the heck out of you, then sell you things that don't work," he said. Human growth hormone, for example, is advertised as a way of turning back the clock. Growth hormone is comparable to estrogen and testosterone, which decrease as women and men age. In theory, resupplying the body with those hormones in the form of human growth hormones will add muscle and lean tissue while reducing fat, in effect slowing the aging process. Licensed medical practitioners, as well as unsanctioned Internet pharmacies, peddle growth hormone as a wonder drug. But it is not only unethical to prescribe it as anti-aging medicine, Perls said, it is also illegal. And the consensus is that it doesn't work. At best, some medical experts say, growth hormone doesn't do anything that a regular exercise regimen wouldn't accomplish, without the risks and costs of the drug.

The Federal Trade Commission has issued warnings about the so-called anti-aging products. "The promise of worthless or unproven remedies can deter victims from seeking the best available treatments," reads an excerpt from one advisory. "In some instances, particularly in the area of cancer, marketers have even told victims that it is not necessary for them to seek conventional treatment." Even prescription medicines and herbal supplements can pose dangers, Moody said. "For every Salk vaccine, there is a Vioxx problem, a drug that seems to work but has side effects." Although over-the-counter vitamins and supplements may be safe if taken in the proper dosage, they may provide nothing more than a placebo effect. "If they want, their money may be better spent on a good bottle of wine or dinner out once a month," Rubin said. But when people pop megadoses of vitamins, the pills can become dangerous. Moody said that people should be as skeptical of the claims made by peddlers of anti-aging medicines as they are of financial planners touting "can't miss" investments. "It gets back to public education," he said. "People are inundated with 'this just in' news. They think, 'What do I believe?' "

How to live longer

For boomers, Moody said, the lesson on aging is simple. "If we're banking on better living through chemistry, we're on a dangerous road." Here's the prescription from gerontologists: "The best way to maximize longevity is to do all the stuff your mom told you," Austad said. "It's the platitudes you heard from childhood -- don't smoke, don't eat too much, and exercise. And go to the doctor." Perls uses ageing, the British spelling of aging, as an acronym to convey how to add years to life. "A" is for attitude, having a positive outlook. "G" is for genetics. People should be aware of their "pedigree" and take preventive measures if they have a family history of terminal disease. "E" is for exercise, six or seven times a week, for at least 30 minutes a day.  "I" is for interest, which Perls describes as remaining engaged mentally. "Exercise the brain, not just the body," he said. "Learn a new language or how to play an instrument. Take up chess or bridge." "N" is for nutrition, which includes getting to a lean weight and maintaining a balanced diet. Eat junk food on occasion as a reward, he said, not as a dietary staple. "G" is for getting rid of smoking and stress. The latter is the harder part, Perls acknowledged. Stress cannot be eliminated, but it can be managed. It's never too late to turn over a new leaf, or get off the couch, said Janice Knebl, chief of the Division of Geriatrics at the University of North Texas Health Science Center at Fort Worth. "You can start at 65 and get benefits." She calls this preventive geriatrics, the process of aging well. "I don't like the term anti-aging," she said. "It's wrong to deny aging. It's a part of life. With aging comes wisdom. "What we try to create is a wellness model, to get the most you can out of life."

IN THE KNOW

Web resources

• Alliance for Aging Research, www.agingresearch.org 
• The New England Centenarian Study, www.med.harvard.edu/ programs/necs/ centenarians.htm
• University of Texas Southwestern Medical Center, www.utsouthwestern.edu
• University of North Texas Health Science Center, www.hsc.unt.edu
• World Future Society, www.wfs.org
• American Federation for Aging, www.infoaging.org
• The Living to 100 Human Calculator, www.livingto100.com

Tomorrow

The first wave of the country's 77 million baby boomers is approaching retirement age, and some experts are worried that too many of them are entering their golden years overweight, sedentary and out of breath -- posing a potential burden on society.

HOW WE AGE

And how science may help ease the symptoms

Medical advancements and safety improvements have helped increase the average life span for Americans, leaving us to deal with the more natural aspects of aging. It's harder to read without glasses. Our knees ache when we get out of bed on a cold morning. We may be short of breath after taking the stairs. Most of these are part of the normal aging process, but there is plenty we can do, personally and through medical science, to improve our quality of life as we age.

Eyes

The lens becomes less elastic with age and cannot change shape as easily to help with near vision. In addition, the lens becomes denser, making it harder to see in dim light, and the eye adapts more slowly to changes in light. Fighting back: Monovision, in which one eye is corrected for near vision, provides some ability to see close objects without reading glasses. A new cataract replacement lens known as crystal lens does that one better, moving naturally with the eye and providing a much wider range of vision. Lens: The normal, clear lens acts to allow fine-focus on images. A cataract is a cloudy condition in the lens that can occur with age.

SOURCE: Atlas of Human Anatomy, Frank H. Netter

Brain

Changes in the brain's message system can result in longer reaction times and some declines in short-term memory. Vocabulary, however, increases until people are in their 80s, which suggests that cognitive changes are complex. Fighting back: The latest research shows that people who remain engaged socially, who continue to challenge their mind and who are more physically active are less likely to suffer from dementia and other mental problems. One of the hottest areas of medical research, according to the American Association of Retired Persons, is memory improvement through chemistry. In other words, a pill might someday ease memory loss.

Ears

A loss of nerve endings and deterioration of ear structures lead to difficulty in hearing high-pitched sounds. Because consonants, which help people identify words, are typically higher pitched than vowels, speakers seem to be mumbling. Fighting back: Researchers at Massachusetts General Hospital recently identified a gene that prevents regeneration of vital inner-ear cells, known as hair cells. By "turning off" the gene, probably with drugs, the researchers believe that hearing could be recovered. Cochlea: Tiny inner-ear cells known as hair cells in the cochlea vibrate and generate signals that are transmitted to the cochlear nerve and on to the brain for processing. Hearing suffers as the number of cells declines due to injury or aging.

SOURCE: The Children's Atlas of the Human Body

Muscles

A decrease in muscle fibers, perhaps because of lower hormonal levels, and a slowing of muscular contractions cause a loss of strength. That loss, combined with changes in the bones, can affect mobility and the ability to perform the basic tasks of living. Fighting back: Recent studies have shown that weight training can slow or reverse muscle loss, allowing older people to be more independent.

Heart and blood vessels

The heart and arteries thicken and become less elastic, which can increase blood pressure and force the heart to work harder. The heart's capacity -- its maximum rate -- drops, as does the body's capacity to consume oxygen. Thus, older people cannot respond as quickly or as well to stress from exercise or illness. Fighting back: Vigorous physical exercise can markedly improve heart function. In addition, more aggressive treatment of high blood pressure could help slow some of the normal aging processes. Aorta: The main artery carrying blood from the heart becomes thicker and less flexible with age. Pulmonary valve: Age thickens the heart valves, including the pulmonary valve, which helps send blood to the lungs to be oxygenated. Left ventricle: The walls of the heart may thicken, decreasing the amount of blood the chambers can hold. This is particularly evident in the left ventricle, which provides the high-pressure pumping action that sends oxygenated blood to the body.

SOURCE: The Human Body Explained

Skin

Normal aging leaves skin thinner, less elastic and more lined. Most other effects, including spots and leathery or yellowing skin, are a result of long-term exposure to the sun. Fighting back: Prevent sunburn and wear sunscreen and protective clothing outside. Eat well, stay hydrated and keep skin moist with lotions.

Bones and joints

Bones become less dense, particularly after menopause. The cartilage that cushions joints thins, and the ligaments that connect bones become less flexible, creating pain with movement and increasing the chances of injury. Fighting back: Weight-bearing exercise can help. Adequate calcium intake at younger ages is important because the body's ability to absorb the bone-building mineral decreases with age. Researchers in nanotechnology have discovered a process that could help create better artificial joints for worn-out knees and hips. Cartilage: The protective coating, shown here in blue, that allows the bone to slide smoothly in a joint becomes dehydrated and thins with age, creating pain with movement. Cartilage does not regenerate.

SOURCE: Look at Your Body: Skeleton

SOURCES: The Merck Manual of Health and Aging; National Institutes of Health; Alliance for Aging research; Dr. Craig Rubin, director, Mildred Wyatt and Ivor P. Wold Center for Geriatric Care at UT Southwestern Medical Center; George A. Kuchel, M.D., FRCP Director, UConn Center on Aging, chief, Division of Geriatric Medicine, University of Connecticut Health Center; The Associated Press; www.medlineplus.com; The American Geriatrics Society

Growing older

Some milestones of aging:  Around 30: Loss of muscle mass begins. Women, for example, typically are 35 percent fat at age 30 and 53 percent fat at 80, although exercise can reverse such changes even late in life. Kidney function begins declining, which eventually can interfere with the body's ability to process medications. Around 35: Bones begin to lose minerals faster than they can be replaced, which can lead to brittle bones and osteoporosis. In women, bone loss is steepest in the first years after menopause. Between 40 and 50: Eyesight changes, making it more difficult to see up close. After 50: Menopause typically occurs between 45 and 55. For men, testosterone levels can begin to decline after age 50. Around 60: We need as much as three times more light to read than a 20-year-old. Mild hearing loss occurs. After 60: The number of cells in the spinal cord begins to decrease, which can create a loss of sensation, such as the ability to feel vibrations. After 70: It could become harder to visually distinguish fine details. After 80: Hearing loss can become more severe.