Popcorn is a very dehydrating snack. Dry foods like popcorn are diffcult to digest, since the digestive system has to come up with a lot of fluids to process it. If refined oil has been used, it is coated with transfatty acids. If salt is added, it further comlicates digestions. Table salts affect assimilation of foods, raise blood pressure and cause kidney congesiton. Kapha types are the only bod types suited for eating popcorn, due to its lightness. However, they don't do well with salt and oils, if added. If popcon is prepeared in the microwave oven, it is outright harmful for everyone. If eaten in between meals, it affects the stomach lining.
The best foods to snack on are fruits, since they pass right through the stomach into the samll intestine (20-30 minutes) without jumpstarting the stomach.