If you need to ask, you're probably not doing enough.
Wow, that was a really aggressive reply, and wasn't meant to be. I often don't do enough and have wondered the same. I think that if it of concern to you, alleviate those concerns by doing more until you feel healthy - then maintain.
Alternatively, listen to a physical fitness instructor type person, rather than my inane suggestion.
How does 3 mile run, one weights session and one core stability session a week sound? Do-able?