Any actual, real-world implementation of such a thing would 1) not be privacy preserving (except in the "we pinky promise we're not going to use this data!" kin

Any actual, real-world implementation of such a thing would 1) not be privacy preserving (except in the "we pinky promise we're not going to use this data!" kind of deal), and 2) would inevitably expand the definition of "unhealthy lifestyle" over time as a way to exclude undesirables from the system and thereby leave more resources for those who remain.