Definitely a movie, in English. Saw it around 6 years ago. It’s a movie where a group of friends go to an island and party all the time. Someone on the island however is slipping drugs into them, and makes them all drowsy and loopy. Soon they find out there is a killer who is murdering people and hanging them around for display. I remember a specific scene where a guy and a girl need to hide under a bed to escape the killer, and the chubby guy says some voodoo words to make himself skinnier in order to fit under the bed.
Maybe Club Dread (2004)