It's not postmodernism. It's pretty standard Frankfurt school fare, which sees humans as defining themselves through the commodities they possess and consume (in this case the products of the fitness industry). The fellow is talking a kind of commodity fetishism, really. https://twitter.com/HPluckrose/status/1006132279905792000 …
Even that Foucault bit is only very uneasily postmodern. There's too much "power over", the Marxist references (neo-liberal capitalism) are too much to the fore, the capitalitzed "Other" - okay, so there's Levinas and Lacan, but also Hegel, Sartre, etc. Foucault's an odd fish.