Intuitively, it stands to reason that overall health affects your sex life. It is a bodily function, after all.
In my own experience, my doctor told me a couple years ago that my LDL level was getting borderline high, so I made some significant changes to me diet. I started making it a point to hit my stationary bike, too, but still not as regularly as I should.
I'm just a scrawny little shit to begin with, but I still ended up dropping like 10-12 pounds. While I haven't noticed any difference in my sex drive, my erections do seem to have powered up a bit despite my age (mid-40s). That extra half-inch of length I used to only get on a really good day is now more an everyday thing. Not that a half-inch has a whole lot of practical value, but it's an indication of overall realized potential.