I gotcha. I agree with you 100% -- the body is an amazing thing. Despite just about every article I've ever read or seen on the subject, I absolutely believe a person can lose fat and gain muscle at the same time -- it's all dependent on the body's ability (or willingness) to tap into fat stores for energy, and keeping your body in that state during your cardio training. Too high of intensity and the body's going to go for an easier fuel store as opposed to tapping into that fat. I think under very strict exercise and dietary monitoring this feat can be achieved even in some of the more fit athletes. The problem is that it's just so simple to create a caloric deficit or surplus, and under even somewhat non-reliable monitoring methods of caloric expenditure and caloric intake, it's pretty simple to create a slight deficit or surplus and achieve the desired results. Even if you're missing your mark a couple of days, it's the long-term that matters...chances are, if you're being strict in your methods, and you're shooting for a goal, whether you miss it by 200 calories in either direction in a day, at the end of the week, it's pretty likely that you've come close. Even still, in the end, whether you can lose fat/gain muscle at the same time, I still believe that (other factors excluded such as one's ability to properly metabolize those calories, etc), a surplus will result in weight gained and a deficit will result in weight lost -- what the body's doing or how the composition is changing at the end of the day is irrelevant in that specific argument.