I am 5’1″ tall. You may be taller. Yet if we both ordered the same chicken and broccoli in a Chinese Restaurant, the waitperson would not go into the kitchen and say: “One person is 5’1″ and the other is 5’9”. We both would get the same protion. But who is the portion meant for?
Is it for me? I don’t think so. Is it for you? Probably not. Is it for the 250 pound person at the corner table? No.
A portion of food in a restaurant is based on how much they want to charge.
In order to reach (and maintain) your goal weight, you need to know what your portion is so that you can identify it across a crowded plate, across a crowded room, across a crowded buffet table.