The RMS value of a continuous function or signal can be approximated by taking the RMS of a series of equally spaced samples.

Although the global figure of domestic resource flows is a rough estimate, it is the most plausible one, given the fact that data are often incomplete and not entirely comparable.

That's based on diet intake surveys, it's based on levels of obesity, it's based on a range of factors that gives you an approximate guess as to how much food is actually going into people's mouths.