Crunches alone won't flatten your stomach, because there are no exercises to reduce fat in specific areas of your body.
If You Stop Working Out, Your Muscle Turns to Fat
Muscle turns into fat only in very rare circumstances, and it never occurs in healthy people.
Eating Protein After a Workout Will Build Muscle
"That's definitely a myth," said Elisabetta Politi, a nutrition director at the Duke University Diet and Fitness Center. "What you need after a workout are carbohydrates."