As a nutritional counselor I have conversed and worked with many people about typical american diseases that so many seem to have. A couple of misconceptions are that 1. it is genetic and there is nothing you can do to change your genes and 2. Getting lots of exercise like competitive running or cycling will make up for poor eating habits.
1. Diseases such as diabetes, heart disease and most cancers are food-born illnesses. Genes determine which one(s) you get. Genes do not act alone, you need unhealthy food to activate them.
2. Exercise is so important on so many levels and if you are motivated enough to get in shape and become competitive that is fantastic! Unfortunately there are so many talented athletes that eat so much crap and they think they can because they burn it off. Even Ryan Loche realized that eating at McDonald's was never going to allow him to beat Michael Phelps at the 2012 Olympics. All the exercise in the world will not prevent or reverse self-inflicted disease, only changing to a plant-based no-oil lifestyle will allow for you to reverse your present or soon to be illnesses.