Free gym memberships are unlikely to result in higher use. I've had multiple workplaces where gym is free and I've rarely used it, thankfully, I am blessed with a skinny physique and parents who inculcated good food habits. In fact, places which charged for gyms explicitly saw slightly higher usage since some folks logic went, since I am paying for it, I might as well get my money's worth.

American health care plans are starting to offer financial incentives for maintaining fitness.

Which seems a bit like a tragedy of the commons situation.

In that insurance company X is paying me for later life benefits that may be reaped by insurance company Y that I have 40 years from now.

We need to hurry up and get to baseline genetic risks, then directly rebate insured out of a central pot if they exceed their expected fitness metrics.