Can goldfish die from overeating, not overfeeding?

yes it is true. Goldfish along with a few other types do not know when to quit eating. It is best to only give them the ammount they need to eat for the size of the fish. If you have several goldfish and one seems to get all the pellets, then try switching to flakes so all have an equal chance to eat. Happy Fishkeeping!!

it can cause bloat and swim bladder disorders, try a google search on the proper feeding methods for goldfish.