Abstract P268: Weight Change is a Poor Predictor of Change in Body Fatness in Cardiac Rehabilitation Patients

Abstract

Introduction : Obesity is a common risk factor in cardiac rehabilitation (CR), yet many CR patients do not realize significant weight loss, despite engaging in regular exercise training while in CR. Hypothesis : We hypothesized that standard CR would demonstrate favorable body composition (BC) changes even in the absence of weight loss and sought to measure the performance characteristics of weight loss to predict BC changes. Methods : We included consecutive patients enrolled in early outpatient CR who underwent air displacement plethysmography with measurements of height, weight, and waist circumference at initiation and completion of CR. We calculated the accuracy of weight loss to identify significant improvements in BC. Results : Data from 112 patients were available for analysis; mean age 60±12 yr., 76% male, mean body mass index (BMI) 30.2±5.3 kg/m 2 . The indication for CR was myocardial infarction (n=33), percutaneous coronary intervention (n=29), coronary artery bypass or valve surgery (n=45), and heart transplant (n=5). Repeat testing occurred after a median of 81 days and 21 phase II CR sessions. There was no change in BMI (-0.53±1.3 kg/m 2 , p=0.43) and weight (-1.6±4.0 kg, p=0.51). Fat mass showed a borderline significant decrease of 2.9±3.9 kg (p=0.08). However, BC improved significantly as measured by body fat % (-2.5±3.2%, p=0.03) and waist circumference (-4.6±5.2 cm; p=0.01). There was a correlation between weight loss and fat mass loss (r=0.85, p=0.0001, positive predictive value=0.94), and % fat change (r=0.67, p=0.0001, positive predictive value=0.91). See table 1. However, the negative predictive value to detect no fat change for patients who did not lose weight was low (0.49, when assessed by % body fat loss, and 0.57, when assessed by fat mass loss). Among patients who did not lose weight, 29 (51%) had a greater than 1% body fat loss. Conclusions : The diagnostic performance of weight change to predict favorable BC changes is poor and highlights the potential utility of BC measurements in the CR setting. Table. Diagnostic Characteristics of Weight Loss as a Predictor of Improvements in Body Composition Weight Loss (kg) Body Fat % Loss ≤ 1% Fat Mass Loss (kg) > 1kg > 1% ≤ 1kg > 1kg 49 5 51 3 ≤ 1kg or gain 29 28 25 33 Sensitivity 0.63 0.67 Specificity 0.85 0.92 PPV * 0.91 0.94 NPV ** 0.49 0.57 * PPV = Positive Predictive Valve, ** NPV = Negative Predictive Value