What are the factors in age-related disease that I can control?

You are wise to look for ways to reduce the impact that aging has on the human body. During the natural aging process, we tend to lose muscle mass over time. Thus, it is important that you do both resistance (strength) training and aerobic (cardiovascular) conditioning on a regular basis. Consider setting aside a minimum of 1/2 hour each day to exercise, and alternate daily between strength training and cardiovascular training. If you do this, and stick to it, you will minimize the effect that aging will have on the loss of your muscle mass. Good luck.