(FORTUNE Magazine) – THEY MAKE your lip curl when you see them in the elevators at the office: those gaunt, humorless guys with gym bags who run a few dozen miles during their lunch hour before breezing through 400-pound bench presses, after which they down a chaste salad and sprint back to their desks. None of that health nut stuff for you -- you're saving your energy and willpower for getting the job done. Besides, you cut out eggs and bacon, limit yourself to two or three business lunches a week, eat dessert only on special occasions, and never get sick, so you're good for another 20 years in the saddle before retirement, right? Good luck. Like most desk potatoes, you are probably in worse shape than you think. Says Dr. William Castelli, head of the Framingham Heart Study, a vast research project on the causes of heart disease: ''If you eat out for a living, you're as good as dead.'' Literally half of all the illnesses and mishaps likely to hobble or kill you are linked to lifestyle and are therefore preventable or eminently postponable. You already know that you should quit smoking, watch your diet, and bestir yourself to exercise occasionally. But myths and misinformation about food, exercise, high-tech annual physicals, and stress abound in lethal doses, even among fanatics in track shoes who should know better. It may be time to hunker down and figure out what works and what doesn't. Don't be surprised by your ignorance. According to Castelli, half the doctors running in the Boston Marathon have cholesterol above safe levels and don't know it. Even if you wanted to, staying fat, dumb, and happy is becoming increasingly difficult. Entire corporations are getting caught up in preventing illness among their workers (see box). AT&T, Saatchi & Saatchi Advertising, and Tenneco have set up comprehensive wellness programs for their employees, installing elaborate athletic facilities, screening thousands of employees for signs of medical trouble, and educating workers on ways to reduce the risk of serious illness. Johnson & Johnson is so convinced of the benefits of its own ten-year-old health program that it created a company in 1987 that provides fitness programs and health education to other companies, including General Motors and General Dynamics. WHY BOTHER paying attention to health, when sausages, sofas, and smokes beckon so seductively? First the bad news. Cardiovascular disease kills virtually half the people in the United States; if it doesn't get the guy at the next desk, it will get you. This year 1.5 million Americans will suffer a heart attack, and 500,000 will die -- 300,000 before reaching a hospital. Some 45% of the coronaries will hit people under 65. Strokes will kill another 150,000. Most are preventable. Says Dr. Edward Schneider, a gerontologist at the University of Southern California: ''A hundred years from now, people will look back on this century and realize there was an epidemic of heart disease in the Western world that was unique in history.'' Why? Just when antibiotics were wiping out infectious diseases, widespread prosperity allowed the masses rich food and sedentary lifestyles. No one is immune. It is true that senior executives get heart disease about a third less often than most employees, according to Medstat Systems, an Ann Arbor, Michigan, consulting firm that reviewed insurance data for FORTUNE on 117,400 workers. But the reason may be that executives are more likely to take steps to reduce their risk, not that white-collar jobs confer any immunity to the dangers of a late-20th-century lifestyle. Your risk of cancer is half your risk of heart disease and stroke, but cancer still ranks as the second-biggest killer in the U.S. (see chart). Some one million Americans each year are diagnosed as having it -- excluding rarely fatal skin cancers -- and a mere 40% of those survive five years. Lung cancer is the most common overall, with about 155,000 new cases diagnosed annually, and death results in 85% of them. Colo-rectal cancer rivals lung in frequency but is easier to detect and treat, so average survival rates are more than twice as high and six times better if it's discovered early. Breast cancer is the most common cancer among women and prostate among men. While the statistics are gruesome, the outlook isn't necessarily. Cigarette smoking accounts for 83% of lung cancer, according to the American Cancer Society, and nearly half of all cancer deaths can be prevented with early detection and treatment. PERHAPS THE KEY INSIGHT to take away from all the new research on health: Ultimately, you can't avoid death, but you can postpone what physicians call morbidity, years of debilitating disease and painful decline. In the absence of serious disease, the human body seems genetically programmed to wear out at about 85 years, and medical science does not appear to be on the verge of changing that. People who exercise a lot and watch their diets live, on average, only about two years longer than those who do not, but they live far more pleasant lives. Says James Fries, an epidemiologist at Stanford University: ''The length of life is fixed, but the time we get sick is malleable.'' Fries wants health programs to stop trumpeting possible gains in longevity and instead emphasize that morbidity can be compressed. Telling someone he will live to 76 1/2 instead of 75 if he jumps on a treadmill is not a powerful motivator, Fries says. ''The more immediate benefits should be stressed. Women who smoke get wrinkles sooner. Someone in his 50s who runs regularly has more energy, has a better sex life, and can work longer hours than someone who doesn't.'' Maintaining your health requires effort, but there are simple steps that can make a big difference. For example, one of the easiest ways to reduce risk of heart attacks is taking aspirin. Starting in 1982, Harvard University researchers conducted a study of 22,000 healthy doctors and discovered that the 11,000 who took one aspirin every other day for five years had 44% fewer heart attacks than the doctors on a placebo. Every male 40 or older should talk to a doctor about taking an aspirin on alternate days. The pill slows the formation of clots that can trigger attacks. It is far from omnipotent, though. Says Charles Hennekens, the Harvard Medical School physician who ran the study: ''A middle-aged man who takes aspirin without cutting out smoking gets much less effect.'' It is numbingly obvious that you should give up cigarettes, but since nicotine rivals heroin and cocaine as an addictive substance, that is easier said than done. In case you forgot: Smoking is the leading avoidable cause of death and morbidity, and the biggest culprit in heart disease and cancer. Even people in the tobacco business may be getting the message. Andrew H. Tisch, 40, the new CEO of Lorillard, which makes Kent, Newport, and True cigarettes, does not smoke. ''He's on a real health kick,'' says Sara Ridgway, a Lorillard spokeswoman. ''He plays tennis and swims and bikes and runs.'' TWO CIGARETTES a day doubles your risk of contracting lung cancer over 30 years, three triples it, and so on up to 20. According to some studies, two years after you stop smoking, your chances of a heart attack return to normal, and ten years later the added risk of lung cancer virtually disappears. Most people quit cold turkey. For those whose problem is severe and intractable, the Smoking Cessation Center at the Mayo Clinic in Rochester, Minnesota, offers hope. The center is experimenting with stick-on patches that release nicotine into the blood through the skin. Another patch containing an antihypertension drug is sometimes used to control withdrawal symptoms. You must be referred for treatment by a doctor. The head of Mayo's smoking center, Dr. Richard Hurt, says 30% of his patients have stayed off cigarettes for a year -- a success rate four times better than that achieved by going to your family doctor for nicotine gum and advice. If you don't smoke, cholesterol is the greatest threat to your health because it clogs arteries and causes heart attacks. Says Dr. Castelli of the Framingham heart study: ''We want all Americans to find out their cholesterol levels. Now that there are portable machines to monitor it, people should be stopped in supermarkets and office hallways to be checked.'' While some critics question whether nationwide cholesterol testing would prolong lives, Castelli believes widespread screening will reduce heart attacks the way screening for high blood pressure begun in the early 1970s cut strokes. As scientists have come to understand, there are two varieties of cholesterol. One variety, low-density lipoprotein, ''is the most vicious kind,'' says Castelli. ''The more there is in your blood, the greater the risk of heart attack.'' LDL cholesterol carries fats through the bloodstream and deposits them in blood vessels, where they block the flow of blood. The good kind, high-density lipoprotein, carries fats back to the liver, where they are eliminated. You want a high ratio of HDL to your total cholesterol. The blood test you might get at the mall can't distinguish the types of cholesterol, but it reveals plenty about how much of it is in your blood, and may jolt you into having more extensive tests done. If your cholesterol level is below 200 milligrams per deciliter of blood, you don't have much to worry about. Check again in five years. FOR EVERY 1% RISE in your cholesterol above 150, your risk of heart attack rises 2%, says Castelli. The average heart attack victim in Framingham has a level of 225. But before you panic, remember that if your total cholesterol measures 220, but your HDL is 65 mg/dl, your risk of heart attack is half the national average for men. An HDL level of 45 puts you at average risk, and 30 means your odds are 80% above normal. If you measure between 200 and 240, get tested for the good cholesterol, and hope you've got enough. Over 240, you are in trouble regardless of what your HDL level is. See a doctor. Start a comprehensive program to get your overall cholesterol count down -- diet and exercise are best, but your doctor may prescribe such drugs as Lovastatin and Gemfibrozil for a stratospheric count. Though young women rarely suffer heart attacks because estrogen slows the buildup of cholesterol in their arteries, they catch up with men in terms of risk six to ten years after menopause. < If you're like most people, you probably think eliminating cholesterol-laden food from your diet will solve whatever problem you may have. It won't, because a bigger villain is saturated fat. Only a third of the evil coursing though your arteries comes from cholesterol in the foods you eat. The rest comes from saturated fat, which the body converts to low-density lipoproteins, the bad stuff. Cholesterol in food is but one variety of dangerous fat. Other varieties are abundant in what we eat, even in many cholesterol-free vegetable oils, making some of them as deadly as cholesterol-laden lard and butter. The worst: coconut, palm, and palm kernel oils, which are popular in food processing because they don't have much flavor of their own and are stable enough to give nondairy coffee creamers, snack foods, and some frozen yogurt a long shelf life. More benign oils such as corn, cotton, and soybean are often saturated by a process called hydrogenation, which boosts the oil's shelf life but has the opposite effect on the people who eat it. Most Americans consume 40 grams of saturated fat a day, chiefly in dairy products, red meat, margarine and cooking oil, and junk food. They should be eating no more than 22 grams. Once you know about saturated fat, many foods you may have thought dangerous turn out to be positively healthy. Shrimp, scorned for years because it has more cholesterol than cheddar cheese, has so little saturated fat (0.3 grams in three ounces) that Castelli recommends it. Lobster (0.1 grams in three ounces, without butter) is clearly better than marbled beef (11 grams in three ounces) or even skinless white chicken (one gram per three ounces). You can eat oysters (one gram in six blue points) and clams (0.2 grams in six little necks) with relative abandon. MOST FISH has almost no saturated fat, and fish or, if the cure isn't worse than the disease, fish oil twice a week might cut heart attack rates in half, according to Castelli. Fish oil and so-called monounsaturated oils such as olive and canola reduce the malevolent LDLs for most people without affecting the good HDLs. Ronald McDonald, on the other hand, seems destined for a coronary: A Quarter Pounder with cheese has a heart-stopping 11 grams of saturated fat. Exercise makes a big difference in how comfortably you age, but you may need less puffing and sweating than you realize. Just about any physical activity, from vigorous gardening and dancing regularly to moderate doses of long- distance running, will diminish your chances of a heart attack. A study of 17,000 Harvard alumni revealed that grads who expended 2,000 calories or more a week in exercise -- the equivalent of walking fewer than three miles a day -- had a 64% better chance of avoiding a coronary than men who did not. There is another little-known benefit to moderate exercise: You get to sneer at fitness fanatics. Dr. Ralph Paffenbarger, author of the Harvard study, determined that burning more than 3,500 calories a week exercising -- running in excess of four miles a day, for instance -- leaves you at just the same risk as someone who walks those two-plus miles a day. It is possible to wear yourself out with too much exercise. Three hours a week of moderate exercise such as tennis, bicycling or swimming is best for most people, says Paffenbarger. As for the age-old debate over whether diet is better than exercise for shedding pounds, ''It doesn't seem to matter how you lose weight,'' says Peter Wood, a professor of medicine at Stanford. Wood put 50 overweight people on diets to lose weight, and another 50 on exercise regimens with no dieting. Dieters lost an average 15 pounds, exercisers 10, but, good HDL cholesterol rose and blood pressure dropped about equally. Exercisers are more likely than dieters to keep the weight off, however, and to maintain the health benefits. Despite follow-up reminders to stick with their regimens, Wood's dieters had gained back half the lost weight a year after the study ended, but exercisers regained only 15%. Why? ''Dieting is complex,'' says Abby King, a psychologist who worked with Wood. ''You eat at least 21 times a week, there are a lot of decisions to be made, and it's harder to do with a friend.'' Exercisers apparently don't experience the same feelings of deprivation that dieters do -- they can eat more and work out with others. Scientists have been doing a great deal of new thinking about stress and its relation to heart attacks. Basically you can chuck those theories about hard- driving Type A personalities being at high risk of coronaries. Most stress, including constant worry that your teenage son seems destined for postgraduate work at Sing Sing instead of the Sorbonne, is not fatal in itself. The real problem is chronic anger. The person who finds himself constantly fuming and yelling at the dunces surrounding him or at the cheats who try to cut ahead in line faces heart trouble. Says Redford Williams, a Duke University internist specializing in stress: ''The rushing-around workaholic is not at risk as long as the stress is not a stimulus for anger.'' He notes that in one study, more than 15% of the 25-year-old doctors and lawyers who scored high in hostility on personality tests were dead by 50. Only some 2% of low-hostility types died so young. The reason: When hostile people get angry, their blood pressure shoots up. Blood pressure for laid-back types stays laid back. Even if what Williams calls ''cynical mistrust'' of others doesn't kill you, it's probably bad for your career. ''A hostile person can fight his way up the ladder,'' says Williams, ''but at a certain point, success on the job depends on leading others and team building, and those things are difficult for a hostile person to do.'' The lesson here: Use exercise to drain off tension, and try being quietly assertive when someone crosses you, instead of blowing your stack. While you know what you can do to ward off heart disease, advice on staving off cancer is maddeningly imprecise. Says Dr. Joseph Fortner, head of the General Motors Cancer Research Foundation: ''The person least likely to get cancer doesn't smoke, doesn't drink or drinks in moderation, and eats a lot of vegetables.'' And there you have it. There is weaker evidence that exercise and holding your weight down help too, says Fortner, but obesity appears directly tied only to uterine cancer. THE ROLE OF DIET is unclear but appears to be a factor in about a third of cancers. The Japanese, for example, suffer far more from stomach cancer than Americans do, but when Japanese come to the U.S., their incidence of stomach cancer drops and colon cancer increases markedly within one generation. After three generations in the U.S., the rate of breast cancer among Japanese women begins to rise. The likely villain is that old devil, dietary fat, according to a Surgeon General's report on nutrition. Vegetables with high amounts of vitamin A, such as broccoli, Brussels sprouts, and carrots, seem to improve the odds against digestive tract cancers. But vitamin A pills are not recommended. Says Charles Loprinzi, a Mayo Clinic oncologist who spent years researching components of the vitamin: ''Perhaps there's a vitamin X in these vegetables we don't know about.'' Some researchers theorize that the roughage in vegetables -- fiber that resists digestion -- helps, and therefore recommend bran and other fiber. ^ Interestingly, the rate of stomach cancer in the U.S. has dropped sharply since the 1930s. One theory as to why: Refrigerators came into widespread use, so people ate less moldy food. Don't bet on a physical exam with a slew of high-tech diagnostic tests to save you from a dissolute lifestyle. Some tests -- notably those for blood pressure and cholesterol, and pap smears and mammograms -- are invaluable. But a massive study of 169 diagnostic tests that was sponsored by the Department of Health and Human Services found that many of the most common ones don't tell doctors anything. ''The average healthy guy or gal having a physical is better off getting information on personal behavior at home and work than undergoing a battery of tests,'' says Dr. Steven Woolf, editor of the Guide to Clinical Preventive Services. AMONG THE MOST COMMON useless tests routinely performed on people without a history of problems: chest X-rays, electrocardiograms, and a lung-function test called spirometry that requires you to blow air into a tube. There is little evidence that chest X-rays provide enough warning to reduce lung cancer deaths. Spirometry is okay for asbestos workers, says Woolf, ''but as part of an executive test, it's probably wasteful.'' Electrocardiograms in people without symptoms of heart trouble, such as shortness of breath or chest pain, don't predict much. A normal EKG doesn't mean you're okay, and by the time the test spots what's abnormal, your coronary arteries are often badly clogged. Moreover, about 25% of routine EKG screenings are falsely positive and often force the unlucky victim to undergo injections of radioactive dye or catheterization to get a clean bill of health. Woolf says women over 40 should be examined for breast cancer annually and have a mammogram at age 50. Other groups, including the American Cancer Society, recommend them earlier. This procedure is not without anxiety and inconvenience: In one of 20 women, according to some studies, the results will indicate that a biopsy is necessary, but only one in five of those will actually turn up cancer. About 140,000 American women will get breast cancer this year, however, and 43,000 will die. But women who have annual checkups are twice as likely to survive the critical five years. Women over 18 should have Pap tests every one to three years. Overworked laboratories often misinterpret Pap slides. The report says that in a survey of 300 labs, Pap smears failed to detect cervical cancers 7.5% of the time. The value of many tests for prostate cancer, the most common cancer in men, and colon cancer, the second most common in men and women combined, is debatable. A digital rectal exam for prostate cancer can't detect many cancers, and can produce about 30% false positives. And there is little evidence that early detection makes much difference. The exam for colon and rectal cancer is embarrassing, scary, and uncomfortable. The patient must endure the insertion of optical probes of varying length in his rectum. For some reason, intestinal cancer is moving farther and farther up the colon, so short rigid probes and doctors' fingers miss a lot. Fortner of the General Motors Cancer Reseach Foundation recommends an entire ''colonoscopy,'' where a scope snakes up to the end of the large intestine. Your family history, and perhaps your tolerance for indignity, should determine how far the tests go. If you insist on a battery of tests, have them at established clinics like Mayo or the Cleveland Clinic, where there are departments set up to handle the procedures quickly and efficiently, with each type of test performed by a board-certified specialist in that field. The Cleveland Clinic uses an artificial intelligence program running on a computer to help determine whether the results of blood tests demand additional examination, but neither place claims to possess unique diagnostic tools. As with many medical procedures, what makes a good diagnostician is having looked at a lot of test results. Says a Mayo doctor: ''If you see 100 mammograms a day, you know what to look for.'' A first physical at the Cleveland Clinic costs about $750 and lasts six hours. At Mayo, it runs between $800 and $1,000 and takes one to two days. Doctors at both facilities are on salary, so there is no financial incentive for them to order unnecessary tests. As doctors at such clinics attest, an important shift is under way in how the medical profession approaches personal health. Says Thomas Kottke, a Mayo cardiologist: ''We have learned the biggest breakthrough in diagnostic medicine is asking people about their lifestyles.'' Herculean attempts to repair the bodily damage that results from years of neglect are giving way to ongoing efforts that will postpone discomfort and decline as long as possible. Nowadays, staying well begins with the realization that wealth and technology have created dangerously easy living. It may seem absurd to deny yourself food ( and work up a sweat for no immediate payoff, but your reward may be a luxury denied all previous generations: a long life of feeling good.

CHART: NOT AVAILABLE CREDIT: SOURCES: CENTERS FOR DISEASE CONTROL, NATIONAL CENTER FOR HEALTH STATISTICS CAPTION: LEADING CAUSES OF DEATH IN THE U.S.

CHART: NOT AVAILABLE CREDIT: SOURCES: OFFICE OF THE ACTUARY, SOCIAL SECURITY ADMINISTRATION CAPTION: EXPECTED LIFE SPAN OF AMERICANS BORN IN . . .

CHART: NOT AVAILABLE CREDIT: SOURCE: AMERICAN HEART ASSOCIATION CAPTION: WHAT YOU GET FOR WHAT YOU SWEAT