Predictive Fat Mass Equations for Children with Inflammatory Bowel Disease

Objective: Evaluate accuracy of skinfold thicknesses and body mass index (BMI) for the prediction of fat mass percentage (FM%) in pediatric inflammatory bowel disease (IBD) and to develop population specific formulae based on anthropometry for estimation of FM%. Methods: IBD children (n = 30) and healthy controls (HCs, n = 144) underwent anthropometric evaluation and Dual-energy X-ray absorptiometry (DEXA) scan, as the clinical reference for measurement of body composition. Body FM% estimated with skinfolds thickness was compared with FM% measured with DEXA. By means of four prediction models, population specific formulae for estimation of FM% were developed. Results: No significant difference in terms of FM% measured by DEXA was found between IBD population and HCs (FM% 29.6% vs 32.2%, p = 0.108). Triceps skinfold thickness (TSF, Model 2) was better than BMI (Model 1) at predicting FM% (82% vs. 68% of variance). The sum of two skinfolds (biceps + triceps; SF2, Model 3) showed an improvement in the prediction of FM% as compared to TSF, Model 2 (86% vs. 82% of variance). The sum of four skinfolds (biceps + triceps + suprailiac + subscapular; Model 4) showed further improvement in the prediction of FM% as compared to SF2 (88% vs. 86% of variance). Conclusion: The sum of 4 skinfolds is the most accurate in predicting FM% in paediatric IBD. The sum of 2 skinfolds is less accurate but more feasible and less prone to error. The newly developed population specific formulae could be a valid tool for estimation of body composition in IBD population and an alternative to DEXA measurement.