From the perspective of the weight-gainer, there’s something socially bizarre about getting fat. About facing, day in and day out, acquaintances for whom fat is a culturally endorsed obsession and yet still a conversational taboo. Next to sex, size might be the thing we think about the most in general and talk about the least in mixed company. Which makes gaining weight, for the gainer, sort of like dyeing an inch of your hair pink each month, both hoping and resenting that no one will mention it. That is, if pink hair could be mitigated by Spanx.

Big Brother is excellently concerned with this and other facets of the American obesity epidemic. The novel is centered on Pandora Halfdanarson, a married stepmother of two who has spent the last few years running a successful business while also settling into the trivial stalemates of a stable marriage (she’s gained weight; her husband Fletcher has…