After eating it, Movement Speed will be reduced by 60% within 60 seconds.

Bad Dumplings are unhealthy dumplings that are currently unobtainable in Survival Mode, but can be grabbed from the Creative inventory. Eating a Bad Dumpling will add 15 Stamina to the player but will also give them a Storm level 1 effect, which will reduce their movement speed by 60% for 1 minute (60 seconds).