Hi Ahtoh, If you saying that people could view this fact as either unfortunate or fortunate, then I see no reason why you can't start your sentence: 'Unfortunately, or fortunately'. It might be a good idea to explain how 'something that could hardly be worse for health' could be viewed as fortunate, but I see no problem with it in terms of English.

No. Something is either fortunate or unfortunate (from a certain perspective). You can voice your disagreement with it in the next sentence, if you'd like. "Trends in behavior could hardly be worse for health. This unfortunate for some, but it doesn't bother me." Or something to that effect.

Your suggestion is not correct because the word "hardly" is a negative word. It means that the trends in behaviour are NOT good for our health.

Ah - from reading your comments on the other answers I think I understand what you mean here. The fact that the situation is so bad that it can hardly get any worse, could be seen as a positive thing - its so bad, it can't get any worse, so that's good isn't it - this is as bad as it is going to get? Well yes, I guess that is one way of looking at it, but it would sound very odd, even perverse to most English speakers to say that it is a fortunate thing that things are so bad they can't get any worse.