How can i eat junk food while staying fit?

Fitness: Fitness is process in which by increasing duration or intensity your body gets more proficient at doing something . Eating is fuel. Whole nutrient dense foods will help where as junk food can hinder the process. If you need to, pick 1 day to eat the junk food. My day is Ftiday night and I eat pizza but Other days I eat to maintain my conditioning. Try limiting to a single day and see.