Why do we dirty a bowl with ice cream, outside of hygienic reasons, when we can create fewer dishes by eating directly out of the pint? Why do we pour chips into a plastic sandwich bag when we can take the entire bag to work and eat directly from it?
Answer: The absence of food tells us when to stop eating, not the quantity.
Only our spoon or fingertips failing to grip remaining morsels of deliciousness make us stop eating. It’s not our stomach or our mind screaming at us to exercise proper portion control that stops our hand from searching for one more bite. Instead, it’s our eyes seeing there is no food left. So, in essence, we are given a portion (the pint, the family size chip bag, the king-size candy bar, etc.), and we decide whether we treat that portion as one serving or more. This is why the words portion and serving are too often used interchangeably. Portion is the amount you are given, not a single serving.
According to Sara Ipatenco’s article, Restaurant Serving Size of Tortilla Chips, a fast-food portion of chips is approximately 280 to 570 calories whereas a sit-down restaurant serves a portion of chips closer to 910 calories.