Fitness Levels Drop More Rapidly after Age 45 Years: Fitness levels drop more rapidly after age 45 years, especially in men, according to the results of a study. However, exercise, maintaining a healthy body mass index (BMI), and not smoking were associated with better fitness levels and cardiovascular health. Andrew S. Jackson, PED, from the University of Houston writes, "The U.S. population is aging and is becoming more obese and sedentary ... and it is well-documented that the cardiorespiratory fitness (CRF) of men and women declines with age and that body composition and habitual physical activity are related to CRF.... Low CRF levels increase the risk of diseases and interfere with older adults' ability to function independently." "These data indicate the need for physicians to recommend to their patients the necessity to maintain their weight, engage in regular aerobic exercise and abstain from smoking," the study authors conclude.  Archives of Internal Medicine. October 26, 2009