Low quality processed food-like products consumed by the masses. Usually high carbohydrate/high fat refined foods, mixed with cheap vegetable oils and fillers.
Example 1.
Friend: Hey Jenny, do you want fries with your steak?
Jenny: No thanks, I don't eat fiat food.
Example 2.
"Brian is fat because all he eats is fiat food. He needs to lay off the carbs and eat some steak".