Re: Is keeping fit part of our responsibilities as believers
Maybe. Certainly FollowingHim is right about it being Wisdom, and Proverbs makes it clear we should seek out Wisdom, and live it. Obviously there's a lot of other 'Wisdom' that many Christians ignore. It's not a salvation issue, of course, but may bring it's own rewards.
Being a good (or bad) steward of your own 'temple' can be a sign of being a good (or bad) steward in other things. This is why Christians didn't smoke when I was growing up. Overeating is the new smoking. I'm trying to quit completely (Overeating, not eating. Or smoking. I quit that as a 10-year-old, after 5 puffs.)