Excelsoir

Hi MrGrim,
A simple but accurate answer to your question is Walking and a Suitable Diet. I am not disagreeing with the suggestions given by the others, but am offering another alternative. You would need to stride out 20 - 30 minutes a day for 3-5 days per week.
You could do some of the strength/endurance exercises as above in-between. The bike is useful too, especially in poor weather. There are various aspects to physical fitness -flexibility, strength, endurance and speed. In your case your will be trying to improve cardiovascular fitness. Exercise also helps improve the High Density Cholesterol ( the "good" cholesterol) as does the consumption of oats, oat bran, almonds and walnuts. A suitable diet avoids fats, especially saturated fats, and processed foods as far as is possible. Fast-food is mostly out, as are a lot of dairy products. Yoghurt is a good substitute. Fish regularly on the menu is very important. Fresh fruit and veges likewise. Anyway, there is plently of info on the 'net re diet. The importance, especially over a long period of time, cannot be exaggerated. Make appropriate diet and exercise an essential part of your lifestyle, especially in view of your family history.Good Luck.
Excelsoir