"Doctors agree that running is good for health."
Translation:Os médicos concordam que correr é bom para a saúde.
Headline speak is different, even in English. But nobody would say the sentence ‘man bites dog’ aloud. (Indeed, this was a joke in the intro of Zak McKracken.) Similarly, in normal text one would normally use ‘os’ here. (And if you're writing headlines, why not go all out: ‘Médicos concordam: correr bom para saúde!’)
@Then it would sound weird: As would ‘Doctors agree: running good for health!’ but that doesn't matter in headline land. Similarly, this sentence without ‘os’ would probably sound weird to most Portuguese speaking people. You can tell by the fact that in virtually every text on-line with this word in this usage it is preceded by ‘os’ (or ‘alguns’, a number or percentage, ‘meus’, ‘todos os’, etc.). If omitting ‘os’ were common, let alone not weird, let alone standard, you'd see more evidence of that; based on what I've found I think I can now safely say that omitting ‘os’ in this case would be an error. Maybe a native speaker could get away with it, but if I would do it, I would just be that silly foreigner who doesn't even know that one should use ‘os’ in this case.