French writer / director Coralie Fargeat's The Substance is a celluloid nightmare of body grotesquerie that floods the screen with more blood and viscera than has ever been presented by masters of repulsion Davids Cronenberg and Lynch.
Demi Moore plays celebrated-film-star-turned-fitness-guru Elisabeth Sparkle, who receives word from her unbelievably sexist boss Harvey (Dennis Quaid) that she's run out of audience appeal and the studio would be looking for someone younger and prettier to replace her.
When Elisabeth follows a murky lead to a solution for aging that will transform her into her "best self," she's introduced to The Substance, a program that offers bodily changes on the cellular level by creating another, separate, perkier version of Elisabeth.
The program warns Elisabeth that she and her alter ego, who takes the name Sue (Margaret Qualley), are limited to a week each before switching back to the other. They can continue this exchange indefinitely, but the time limit rule -- among others -- is not to be broken, which, of course, means it will.
Sue goes to the studio and in short order becomes television's new fitness darling, leaving Elisabeth to sulk and gorge. The experiment soon goes off the rails, as we fully expected, and Fargeat's stunningly imaginative production and sound designs shift into high gear to make fuller comment on dysmorphia and misogyny.
Moore is a wonderful and underrated actress, IMO, who does phenomenal work here as Elisabeth's physical and mental states steadily decay. Qualley (who also appears in Yorgos Lanthimos' latest freak-out Kinds of Kindness) is a fierce presence who handles her highly physical role with enormous commitment even when covered in a hundred pounds of foam and latex.
The Substance is not an enjoyable film, strictly speaking. It is exhausting and revolting, but it is also instructive, insightful, frightening and weirdly funny, so the disorientation and nauseousness are not wholly gratuitous.
Ghastly imagery comprises three-quarters of the film, with the last quarter the true test of the audience's mettle. It will take a lot of fortitude -- and a strong stomach -- to stick with it to the bitter, bitter end.
Don't eat before going.