How do doctors enhance health and resistance to disease?

Knowledge. Pts and drs alike need to do preventive medicine. Have one physical exam a year, get your laboratory tests. Depending your age...Ekg, mammograms, bone densities, colonoscopies, psa. There are many medications for prevention: aspirin, meds for colesterol, vaccines, calcium and vitamin d to prevent osteoporosis, multivitamins if we have poor diets. Encourage to exercise, keep ideal weight , sleep.
Handwashing/exercise. Doctors are not more naturally resistant to disease, they just take precautions in preventing disease. Handwashing is the most important thing doctors can do to enhance health and prevent infections. Many doctors also take advantage of their knowledge of disease prevention and spend time exercising and eating healthy. Prevention is the key.