Not necessarily. It could be that the game can add a bonus to players performance depending on his Fitness, while Condition loss (CL) stays the same.
As we know from Al's guides, CL is the Experience. In the game's mechanics it's the same thing (with multiplier 1.33). So if Fitness affects CL, it should be somehow compensated so players don't progress slowly because of high Fitness skill.
We simply don't know. I hope more tests will clarify this.
Also I'd like to know if I should activate Condition bonus to reduce CL. I suspect the answer on this question will be the same. Or maybe not? ::)