Perfection Protein Powder was designed to read the imbiber's subconscious through neuronal transmitters, and through that, construct a genetic template to superimpose on that user. It worked perfectly.
What it intended to read from the imbiber's subconscious was their idealised body, intended to be aimed at wannabe body builders and jocks and overweight women. That isn't what it read. It looked for a warped ideal of the ideal body that would be possessed by the imbiber's ideal partner, but not even anything so profound as that: it just assembled various ideas James found attractive.
The first change, unnoticed by James, was that his mind had flitted to the show he'd just watched in the waiting room. His head began to morph, the features running and flowing before filling into the shape of the mom on Modern Family. His messy brown hair elongated, into a blonde bob. He had the body of a teenager and the head of a stunning fifty year old actress.
The doctors noticed he hadn't noticed, scribbling down some notes but not alerting someone who, after all, was their test subject. He didn't notice any changes until a few minutes later when his chest began to bulge, and bulge, and distend. He stood up, screaming, screaming louder when rather than his own voice, out came that of actress Julie Bowen. "What the fuck is happening to me?!" he implored the mirror, turning so they could see clearly his slender torso, clearly aged to fifty, but with a pair of huge breasts, larger than his head. They were almost gravity-defying, not sagging, standing pert and bouncy on his chest. The nipples were so full and thick they were better described as teats. He'd always loved big tit porn, and now he had a pair of his own.
He flopped back in the chair, peering between his cleavage to see his cock shrivelling away, his lower half becoming feminine too, completing his shrinking to 5'2''. A hairy bush crowned the pussy forming as his cock finally inverted. "What have you done to me?!" he demanded, but still no scientists rushed into the room.