The best solution for you is to eat healthy foods only and limit fast-foods to a minimum. These are the years that could be very valuable because you now have the golden opportunity to develop healthy eating habits that will stay with you for the rest of your life. In a few years you will marry and raise a family and pass on those healthy eating habits to your children. This does not mean you should totally avoid fast foods; you can allow yourself to occasionally enjoy them. Always remember that you can control what you eat.