If a body weight of X is maintained by a calorie intake of Y then regularly consuming more calories will lead to weight gain and regularly consuming less will lead to weight loss. To me, portion control is about finding the amount of calories required to reach and then maintain a desired body weight. I know when I'm looking at my plate if there is 'too much' on it. Curtailing the amount of carbs is portion control. I can have a huge amount of salad on a plate and very little carbs. Both portions are controlled just.one has to be limited. Portion control is a buzz word for don't eat.so much of the 'bad' stuff. Eat less of what causes you problems.