There are no fat suits in “Gigantic,” the new musical set at a weight-loss camp for bulky teenagers. For its characters, the end of the summer will bring no magical transformation from round to svelte.

The actors in this Vineyard Theater production are bigger than the people you usually see onstage, and there’s something both rebellious and affirming in that. These are talented performers, and at least a couple of them — Ryann Redmond and Max Wilcox, the show’s winsome romantic leads — get to play the kind of roles usually reserved for actors with gym-buffed physiques. In its range of body types, this cast looks a lot more like America than most.

“It’s true, I’m fat, and I fail to see what’s wrong with that,” one lyric goes, but unfortunately that’s about as mutinous as things get in “Gigantic.” The show’s defiantly feel-good message about being comfortable in one’s own skin is in philosophical conflict with its creative impulses, which are otherwise thoroughly conformist.