Doctors should spend more time counseling their patients on how to lead healthier lives through diet, exercise and other preventive means, a panel of health-care experts says.

The report Tuesday by U.S. Preventive Services Task Force also questions the value of routine screening tests and says physicians should reserve use of these procedures for high-risk patients."The key to improved health and disease prevention often lies in lifestyle changes made by patients rather than in the broad testing or sophisticated medical procedures performed by health providers," Dr. Robert S. Lawrence, task force chairman and director of primary care at Harvard Medical School, said upon release the panel's Guide to Clinical Preventive Services.

About 5,000 copies of the nearly 300-page guide are to be distributed to medical educators and societies of health-care professionals. It is expected to be available in medical bookstores by summer.

The guide recommends that physicians counsel their patients who smoke on how to kick the habit, their sexually active patients on how to prevent sexually transmitted diseases and all their patients to engage in regular physical activity.

Doctors should also provide periodic counseling on diet and all patients should be urged to use seat belts and should be warned about the effects of drugs and alcohol, the guide says.

The guide also concludes that routine chest X-rays are ineffective as a screening tool for lung cancer and that electronic fetal monitoring - currently used in more than half of all deliveries - should be used only for high-risk pregnancies.

The panel said it is unclear whether fecal occult blood testing is an effective routine screening tool for co-lorectal cancer or whether digital rectal examinations are an effective test for prostate cancer in men who have no symptoms of the disease.

"Our review of the data has shown that routinely performing a uniform battery of tests on patients is often ineffective in improving health and can potentially lead to large numbers of inaccurate results," Lawrence said.

Lawrence said that a greater emphasis on providing information and patient counseling will require changes in the attitudes of doctors and in the medical fee system. "It's going to be a long, hard struggle," he said.