Editing your own foods
Foods you created are fully yours: open one and tap Edit, or swipe the row in My Foods, and the same three-step editor opens with everything changeable — name, serving, nutrition, barcode. Entries already in your diary keep the values they were logged with, so fixing a food today doesn't silently rewrite last month.
"Editing" a catalog food
Foods from the shared catalog can't be modified in place — thousands of people log the same entry, so one person's correction can't overwrite everyone's data. Instead, choose Edit values on the food: you get your own editable copy, prefilled with the original's data, marked clearly as yours.
Your copy is what you'll log from then on — it shows up in My Foods and in your search results alongside everything else. The catalog original stays untouched for everyone else.
When is this worth doing? A label that changed since the catalog entry was made, a regional formulation with different macros, or a product whose serving size you want defined your way.
Duplicating
Your own foods can also be duplicated from their detail view — handy for creating variants (the same yogurt in two sizes, a recipe's base with one tweak) without re-typing the label.
One rule to remember
If the food's numbers came from you, you edit it directly. If they came from the catalog, you edit your copy of it. Either way, nothing you do reaches other users — unless you explicitly contribute a food to the catalog.