The first thing that needs to be said about Leslye Headland’s “Bachelorette,” at Studio Theatre is that it is part of Headland’s Seven Deadly Plays series, in which single plays deal with human failings: lust, greed, sloth, wrath and envy. “Bachelorette” takes on gluttony.

Without that knowledge, it’s hard to understand Headland’s extravagant, nearly incredible characters, who exist in catty, exaggerated relief while their gluttony utterly dehumanizes them.