I’m not opposed to words having multiple meanings or even skipping around and settling on whole new meanings. As a matter of selfishness, I support polysemy, because my research field is lexical semantics. The more ambiguity, the better, say the ranks of computational linguists needing employment. And language change should be as fast as possible. No, faster.
Nevertheless, after a heated discussion around Health At Any Size/fat acceptance issues (see Don’t You Realize Fat Is Unhealthy? for one statement of what is up with that, note that I’m less competent to argue the merits than Kate Harding, or, possibly, you dear reader, so do your own research) I noticed one ambiguity that got in the way: the word ‘healthy’.
Here’s one definition: a person who is healthy does not have disease.
Here’s another definition: a person who is healthy is doing things correlated (or thought to be) with not having disease, or at least not developing further disease very rapidly.
And people slide around between these all the time, both as a matter of deliberate rhetorical strategy and as a matter of sloppiness. And there is thus some genuine confusion in which people almost slide right along from
I work out three times a week to
I will never die, or, actually, now that you mention it, age. Pretty much no one is completely healthy under either definition of the word, but best efforts under the second do not automatically make you healthy under the first (or vice versa). Nothing will. There is no magic bullet. As someone pointed out to me in an, alas, unquotable location, life, in fact, is something of an anti-magic bullet, in that the greatest risk factor for many diseases is age.
I think the biggest place this confusion happens is people saying
I am so much healthier when they mean either
I am so much fitter or
I weigh so much less. Which becomes a problem when they actually think they mean
I have less diseases now. Only possibly.