It appears to me -- based on research that's available -- that very low body fat percentage around the abdominal muscles is one of the best predictors for health and longevity, with the caveat that this low body fat percentage around the mid-section is due to a low-calorie diet and not steady-state cardiovascular exercise or powerful stimulants (so, for example, marathon runners and cocaine addicts are excluded).
The question arises, however: is CR with fat around the abdominal muscles less effective for longevity and health than CR with very, very low fat around the abdominal muscles? Or to put it another way: if you still have fat around the mid-section are you still doing "enough" CR? I suspect the answer is yes, for two reasons: first, abdominal (and visceral) fat has a hormonal effect on the body; second, abdominal fat is linked to a wide range of aging diseases (prompting some researchers to label stomach fat as the leading indicator for "Syndrome X"). I'm still wondering, however.