I agree about health being a normative notion - in the past I've tended to focus on this specifically in terms of mental health, as in an arguing that those who would deny objective moral values cannot appeal to notions of insanity to disqualify or argue against a given action (this has important consequences for many areas of modern Psychology). In other words there's no option of going halfway with the Nietzschean collapse of value.

I thought Foucault argued along similar lines somewhere?

About it being a problem for the Materialist, if by 'gross' you mean mechanistic then yes. On the other hand a number of atheist philosophers such as Quentin Smith and Evan Fales argue along Aristotelean lines deriving moral conclusions from functions.

I think others are right that the non-Aristotelian secular consensus is that medicine is treated as instrumental to something like comfort rather than having health-as-proper-function as an end.

One sort of case that might be thought to adjudicate between the two theories would be the treatment of "vestigial" conditions (where, by "vestigial", I mean things that don't cause discomfort). It seems as though, where proper function is damaged by no discomfort is caused, it's sometimes intelligible for a patient to forgo treatment, but it's also intelligible for a patient to undergo the treatment; the damage to proper function is just a reason for medical practice, whether or not there is discomfort. On the other hand, I think the former intuition (that it's intelligible to forgo treatment of proper function) is more pragmatic and has to do with one weighing the costs of treatment with the damage.

Here's another thought: Instead of damage to proper function without discomfort, consider discomfort without damage to proper function. The purpose of pain is to alert one to bodily damage. So pain and discomfort are not per se a problem. One would not want to undergo a surgery, say, that prevents certain pain receptors from working (and thereby sometimes prevents discomfort that one would otherwise feel); the prevention of discomfort just isn't a sufficient reason for this. Rather, when medicine aims to prevent or remove discomfort, it should be doing so because discomfort is typically indicative of loss of proper function, that something has "gone wrong" in the full-blooded Aristotelian sense.

So I think the Aristotelian account is pretty defensible, though I'm not familiar with any of the medical ethics literature.

I have seen the Aristotelian conception used to argue that lots of things ("gender reassignment surgery," contraception) do not contribute to health.