Publications from trusted medical and health organizations are the safest places to get information about using exercise to improve health. As of March 2015, organizations such as the Mayo Clinic, the Harvard Medical School, and the Centers for Disease Control and Prevention all provide exercise-related information.
Medical sources often focus on the health benefits of exercise rather than the aesthetic benefits. The Fitness section of the Mayo Clinic website explains how exercise can reduce disease, help control weight and improve coordination at any age. It contains straightforward recommendations for aerobic exercise and strength training, each derived from the most recent medical studies.
Harvard Health Publications, which is associated with the Harvard Medical School, dedicates a significant amount of space to fitness and health. It explains how exercise can improve bone strength, extend life expectancy, alleviate back pain and prevent falls. The website details a four-point fitness strategy that includes aerobic activity, strength training, balance movements and flexibility exercises.
The CDC publishes a fact sheet that lays out the statistical connections between exercise and better health. It focuses heavily on walking, which can be done anywhere with minimal equipment. The CDC website discusses how walking can reduce the risk for specific diseases and health conditions.