What I did to change my diet is just start being more active at the grocery store. Look for foods that are low in saturated fats and have more fiber. If you look at the nutrition label, avoid foods that start with "enriched", or contain "high fructose corn syrup" and "hydrogenated..." and "vegetable shortening" and "vegetable oils". Increase your vegetable and fruit intake, and drink a lot of water. Start by increasing to 40 oz of water per day, and try to get to the point where you're drinking 100 oz per day (more when you start increasing your cycling in the warmer months).
That would be a good start.
Koffee