Determination of cardiorespiratory fitness in metabolically healthy obesity and normal-weight obesity: A cross sectional study

The true cardiometabolic risk of the body composition phenotypes normal-weight obesity (NWO) and metabolically healthy obesity (MHO) remains controversial. Cardiorespiratory fitness (CRF), as measured by peak oxygen uptake during exercise (VO2peak) is inversely correlated with cardiovascular disease (CVD), and it is a strong, independent indicator of cardiometabolic health. Individual components of body composition, including total body fat, visceral adipose tissue (VAT), and lean mass also influence CVD risk, but their impact on CRF is not well known. The objective of this study was to determine VO2peak in NWO and MHO relative to lean, healthy controls (HC), and metabolically unhealthy obese controls (MetS) to determine the impact of body composition on CRF. Participants were recruited into one of four groups based on body mass index (BMI), body fat percent (BF%), and metabolic risk factors: NWO (normal BMI with high BF%); MHO (obese BMI, high BF%, and /= three of the diagnostic criteria for MetS); and HC (normal BMI, BF%, and metabolic markers). Participants engaged in a peak exercise test on a cycle ergometer to determine VO2peak and a DEXA scan to measure body composition. Forty participants completed this study (n = 10/group). VO2peak (ml/kg/min) was greater in HC (44.2 +/= 11.0) compared to NWO (28.4 +/= 5.9; p = 0.001), MHO (25.4 +/= 6.7; p = 0.0001), and MetS (24.6 +/= 10.0; p /= 0.76). There were strong, significant correlations between CRF and VAT (r = -0.66; p< 0.0001) and total fat mass (r = -0.78; p < 0.0001), but no significant correlation between lean mass and CRF. VO2peak did not significantly differ among NWO, MHO, and MetS, and all were lower than HC. This suggests that NWO and MHO have similar cardiometabolic to MetS. The strong associations between fat mass variables and CRF demonstrate the possible impact of body fat on physical fitness. Future research should investigate how changes in fat mass influence CRF in these phenotypes