Ancient Rome Was Infested with Human Parasites, Poop Shows
snip..."Also, many Romans enjoyed eating an uncooked and fermented fish sauce called garum. "Roman enthusiasm" for garum may explain why fish tapeworm parasites were so common in the empire, as the parasites live in fish. (Cooking the fish kills the parasite, Mitchell said.)"
Tinned anchovies have been heat processed.
That probably led to overeating with no weight gain. ;^)