There are many types of indices to consider. The FAO link above is to the Codex A., which focuses on trade regulations, not food security or indices relating to hunger. You probably want to look at the following: a) Article Measuring Household Food Insecurity: Why It's So Important a...
b) Article Measuring malnutrition in all its forms: An update of the ne...
and c) https://www.ifpri.org/publication/concept-global-hunger-index-0.