WONG, S. L., P. T. KATZMARZYK, M. Z. NICHAMAN, T. S. CHURCH, S. N. BLAIR, and R. ROSS. Cardiorespiratory Fitness is Associated with Lower Abdominal Fat Independent of Body Mass Index. Med. Sci. Sports Exerc., Vol. 36, No. 2, pp. 286–291, 2004.
Purpose: To determine whether, for a given body mass index (BMI), men with high cardiorespiratory fitness (CRF) have lower waist circumference (WC) and less total abdominal, abdominal subcutaneous, and visceral adipose tissue (AT) compared with men with low CRF.
Methods: Subjects were categorized into HIGH CRF (N = 169) and LOW CRF (N = 124) groups based on age and CRF measured using a maximal treadmill test. Total abdominal, abdominal subcutaneous and visceral AT were measured by computerized tomography.
Results: For a given BMI, men in the HIGH CRF group had significantly lower WC (P < 0.001), total abdominal (P < 0.001), visceral AT (P < 0.001), and abdominal subcutaneous AT (P < 0.001) compared with men in the LOW CRF group.
Conclusion: These findings suggest that the ability of CRF to attenuate the health risks associated with BMI may be partially mediated through a reduction in abdominal AT. Accordingly, our observations reinforce the importance of regular physical activity in the prevention and reduction of obesity-related health risk independent of a corresponding reduction in body weight.
It is generally accepted that waist circumference (WC) is positively associated with increased morbidity and mortality from Type 2 diabetes and cardiovascular disease (CVD) independent of body mass index (BMI) (12,18). It is also established that cardiorespiratory fitness (CRF) is associated with reductions in all-cause and CVD mortality rates (4). Further, evidence from large observational studies suggests that CRF attenuates obesity-related health risk (30,32). Indeed, it has been reported that low CRF is associated with premature mortality in individuals classified as normal-weight, overweight, or obese, independent of other mortality predictors, including smoking, hypertension, and Type 2 diabetes (32).
The observation that CRF attenuates obesity-related health risk as measured by BMI (14,32) may be explained by differences in abdominal adiposity. Abdominal obesity as measured by WC is a strong marker of metabolic risk and disease independent of BMI (12), and recent evidence suggests that exercise training is associated with a reduction in WC, independent of changes in BMI (26). Further, in a large cohort representative of the Canadian population, it was shown that high CRF is associated with significantly lower levels of WC for a given BMI by comparison with those with low CRF, independent of gender (28). Together, these findings suggest that reductions in abdominal obesity may be a mechanism by which exercise attenuates obesity-related health risk as measured by BMI. However, currently it is not known whether the reduction in abdominal obesity is a consequence of reductions in visceral and/or abdominal subcutaneous adipose tissue (AT). Some researchers report that visceral AT is an independent predictor of metabolic risk (7,25), whereas others report that abdominal subcutaneous AT (1,10) or a subdivision of abdominal subcutaneous AT, such as deep AT (16), is of primary importance. Thus, the extent to which the attenuation of obesity-related health risk by CRF may be explained by a corresponding reduction in subcutaneous and/visceral obesity independent of BMI would add valuable insight into plausible mechanisms.
The purpose of this study was to test the hypothesis that, for a given BMI, men with high CRF have a lower WC and less total abdominal, abdominal subcutaneous, and visceral AT by comparison with men with low CRF.