Providing gym memberships is kind of problematic, if not outright insensitive. Body positivity is a thing and self-love can be expressed in more ways than just this one.
I don’t think that promoting exercise as a component of healthy living makes a statement on body image. People who exercise have all types of bodies, all of which are acceptable.
It is paternalistic to “force” people to go to the gym to receive this compensation for their work. But there’s also plenty of research showing positive benefits of exercise on overall well-being for it to make sense for businesses to incentivize it from a worker performance perspective without body image entering into the discussion.
Seems kind of like an ableist “perk” to me. I understand that it’s one of those things that’s not intended to be, but the net result is still the same.
You really should have led with this argument because "companies shouldn't give employees gym memberships because fat people might not use them" is an awful argument but "companies shouldn't give employees gym memberships because some employees might be physically unable to go to a gym" is pretty reasonable if the alternative is just giving them money instead.