Type 2 diabetes, or adult onset diabetes, is a complex condition which involves the interaction of both environmental factors with genetic factors. Without a doubt there is a strong genetic component, and so the fact that no one in your family has diabetes is good. However, the development of diabetes should be thought of as a series of conditions which make your body unable to process glucose well, conditions like being sedentary, eating a diet high in processed refined carbohydrates, and being overweight. In people with a genetic predisposition, they develop diabetes under these conditions more quickly, but anyone who lives in these conditions can eventually develop diabetes even though they might not have a genetic predisposition.
Therefore leading a healthy lifestyle is the most important way to prevent type 2 diabetes. This includes regular exercise, keeping the weight within acceptable limits, and eating a healthy diet. If you stop exercising, you will not immediately develop diabetes of course, but healthy habits are definitely what prevent it over the next several decades of your life.
If you have any other questions about preventative health or diabetes you should feel free to talk to your primary care doctor
, who is an expert in these things!