BackgroundAnalysis of body composition is becoming increasingly important for the assessment, understanding and monitoring of multiple health issues. The body mass index (BMI) has been questioned as a tool to estimate whole-body fat percentage (FM%). Recently, a simple equation described as relative fat mass (RFM) was proposed by Woolcott & Bergman. This equation estimates FM% using two anthropometric measurements: height and waist circumference (WC). The authors state that due to its simplicity and better performance than BMI, RFM could be used in daily clinical practice as a tool for the evaluation of body composition. The aim of this study was to externally validate the equation of Woolcott & Bergman to estimate FM% among adults from north-west Mexico compared with Dual-energy X-ray absorptiometry (DXA) as an alternative to BMI and secondly, to make the same comparison using air displacement plethysmography (ADP), Bioelectrical Impedance Analysis (BIA) and a 4-compartment model (4C model).MethodsWeight, height and WC were measured following standard procedures. The RFM index was calculated for each of the 61 participating subjects (29 females and 32 males, ages 20–37 years). The RFM was then regressed against each of the four body composition methods for estimating FM%.ResultsCompared with BMI, RFM was a better predictor of FM% determined by each of the body composition methods. In terms of precision the best equation was RFM regressed against DXA (y = 1.12 + 0.99 x; R2 = 0.84 p<0.001). Accuracy (represented by the closeness to the zero-intercept) was 1.12 (95% CI: -2.44, to 4.68) and thus, not significantly different from zero. For the rest of the methods, precision in the prediction of FM% was improved compared to BMI, with significant increases in the R2 and reduction of the root mean squared error (RMSE). However, the intercepts of each regression did not show accuracy since they were different from zero, for ADP: -9.95 (95%CI: -15.7 to -4.14), for BIA: -12.6 (95%CI: -17.5 to -7.74) and for the 4C model: -13.6 (95%CI: -18.6 to -8.60). Irrespectively, FM% measured by each of the body composition methods was higher for DXA than the other three methods (p<0.001).ConclusionsThis external validation proved that the performance of the RFM equation used in this study to estimate FM% was more consistent than BMI in this Mexican population, showing a stronger correlation with DXA than with the other body composition methods.

Background and objectives: Body composition assessment can provide information associated with breast cancer patients’ (BCP) prognosis, that can lead interventions to improve survival outcomes. The aim of this study was to evaluate the effect of an individualized nutrition intervention program on breast cancer patients using bioelectrical impedance vector analysis (BIVA). Materials and Methods: This is a pretest-posttest study in recently diagnosed nonmetastatic BCP undergoing antineoplastic treatment, free of co-morbidities and dietary supplementation. Body composition was assessed at baseline and 6 months after an individualized nutrition intervention program, by dual-energy X-ray absorptiometry and BIVA. According to BIVA, each participant was located in the bivariate tolerance ellipses for Mexican population (50%, 75%, and 95%). In clinical practice, the 50% and 75% ellipses are considered within normality ranges. Results: Nine nonmetastatic BCP completed the intervention and were included in the analysis. After the intervention, they decreased by 5.8 kg of body weight (IQR, 3–6; p < 0.05), 3.8 kg of fat mass (IQR, 0.1–4.2; p < 0.05), and 1.4 kg of fat-free mass (IQR, −0.1 to 4; p < 0.05) while appendicular skeletal muscle mass remained unchanged (−0.2 kg, IQR, −0.8 to 2.3; p = 0.4). Using BIVA at baseline, five participants were among the 50% and 75% ellipses, mainly located in the area corresponding to edema and low lean tissue, two in the cachexia quadrant and two in the athletic quadrant (≥95% ellipse). After 6 months of intervention, six out of nine participants were in the athletic quadrant and eight of nine BCP were above the 5° phase angle cut-off point. One patient initially presented cachexia (≥95% ellipse); at postintervention her vector changed to the 50% ellipse. Conclusions: An individualized nutrition intervention program designed for nonmetastatic BCP was effective to improve the nutritional status of BCP as assessed by BIVA, therefore BIVA can be a useful tool to monitor changes in nonmetastatic BCP body composition in research and clinical practice.

Body composition assessment by bioelectrical impedance analysis (BIA) in breastfeeding women can provide an insight on the changes in body tissues and the state of hydration. Our general aim was to assess the changes of BIA parameters in overweight or obese breastfeeding women after an individualized nutritional intervention. After an informed consent was signed, breastfeeding women (2–8 weeks postpartum) were randomly assigned by simple allocation in blocks (1:1) to either the intervention (In) or control (Cn) group. These two groups received general recommendations on healthy eating during the lactation period; additionally, the In group received a dynamic menu with meals based on equivalent interchangeable foods every 2 weeks for 3 months. Body composition was evaluated using anthropometry and multi‐frequency bioelectrical impedance (Impedimed™) at baseline and 3 months after the intervention. Out of 345 women invited, 37 were eligible but only twenty (n = 10/group) completed the intervention program. At baseline, there were no differences in age and body mass index (BMI) and 60% of both groups of women declared exclusive breastfeeding. At the end of the program, the In group showed differences of −2.9 kg of fat mass [IQR −7.1– −0.9 (p<0.05)], −2.5 cm in waist [(IQR −5.0 – 0.2 (p=0.06)] and −3.2 cm in hip circumferences [IQR −4.7– −1.7 (p<0.05)]. Change in resistance standardized by height was ‐ 27 ohms [IQR −63–0.7 (p<0.05)]. Fat free mass and total body water remained unchanged with medians of +1.4 kg [IQR −0.15–2.6 (p=0.4)] and +0.95 kg [IQR −1.5– 3.2 (p=0.1)], respectively. This individualized nutrition intervention program designed for breastfeeding women was effective in improving the mother’s body composition. Multi‐frequency BIA can be a useful tool to monitor these changes during postpartum subjects in clinical practice. This trial was registered at clinicaltrials.gov NCT03640104. Support or Funding Information LT, AGP, JCV recieved a fellowship from The National Research Council (CONACYT)