How to evaluate obesity-related functional limitation: relationship between cardiorespiratory fitness and anthropometric parameters

Abstract Background The new definition of obesity foresees a combination of anthropometric and clinical parameters considering also functional limitation as diagnostic criteria. The waist-to-height ratio (WHtR) has been proposed as a more accurate anthropometric index in identifying higher cardiometabolic risk, but the functional limitation is less clearly defined. Cardiopulmonary exercise test (CPET) is the gold standard method for assessing functional capacity Purpose To evaluate the relationship among different anthropometric parameters including WHtR and CPET parameters in patients with obesity. Methods This is an observational study involving adults living with obesity (BMI 25 kg/m², WHtR 0.5), with or without bariatric surgery (BS) therapy that underwent to maximal CPET. Clinical and anthropometric parameters, including waist circumference and waist-to-height ratio (WHtR), were collected. Statistical analysis included t-test or Mann–Whitney U, Spearman’s rho for correlations, and multivariate regression analyses. Results Among 593 patients with obesity (72.8% women, mean age 46.2 ± 11.3 years), mean BMI was 35.7 ± 6.9 kg/m², WC 112.8 ± 17.9 cm, and WHtR 0.68. VO2peak/kg was significantly (p 0.05) and inversely correlated with BMI (Rho = –0.45), waist circumference (Rho = –0.35), and WHtR (Rho = –0.45). In patients undergone BS, correlations were similar, but WHtR loose the statistical significance. Multivariate analysis corrected for age, sex and percentage of heart rate at exercise peak (were applicable), showed that all anthopometric paramenters had quite similar independent relationship with cardiopulmonary parameters, but also that the percentage of variance explained was low. Nevertheless, BMI demonstrated a quite stronger value of independent determinant of cardiorespiratory fitness (β = –0.497), followed by WC (β = –0.480) and WHtR (β = –0.438). BMI had a higher relationship also with haemodynamic parameters at rest and during exercise during exercise (Systolic blood pressure at rest β = –0.367 ant at exercise peak β = –0.273). Conclusions WHtR, WC, and BMI, despite with a low proportion of explained variance, were all independently associated with cardiorespiratory fitness in patients with obesity, with slight superiority of BMI. WHtR lost its correlation with functional parametes in people undergone to BS. In conclusion, an adequate functional assessment performed using standardised and gold standard methods is an irreplaceable diagnostic tool for classifying patients with obesity.