www.theguardian.com/science/2019/jan/14/nutritionists-launch-portion-size-guide-to-tackle-overeating
This is roughly in line with the portion sizes I've been eating recently in a drive to be healthier - BUT I have been often pretty hungry (not starving, just used to a greater amount of food and having to reset my norms) and it's very very hard to eat out at all and follow these guidelines. I know reading threads on here, for example, many people think 500g of mince will only serve two people in bolognese.