Samenvatting

Background & aims: Overweight and obesity can cause several health risks, and weight loss can help reduce them. However, weight loss in older adults is associated with loss of muscle mass and bone mineral density. To prevent this, it is important to monitor changes in FFM. Bioelectrical impedance analysis (BIA) is mostly used in dietetic practice to measure body composition. The use of BIA requires an equation to estimate the FMM. Since there is no equation for overweight and obese older adults, this study aimed to develop an equation to estimate the FFM for this population. Methods: Data from 275 overweight and obese older adults (55+) were used to develop a new equation for estimating FFM using resistance data of BIA measurements with air displacement plethysmography (ADP) as a reference. Baseline data of 3 lifestyle interventions at the Amsterdam Nutritional Assessment Center (The Netherlands) were used. Multiple linear regression analysis was used to develop a predictive model. The equation was evaluated by analyzing the percentage under-, accurate and overestimates, bias, absolute mean error, SEE, and limits of agreement. Results: A new equation was developed: Predicted FFM (kg) = -21.649 + (7.075 * Sex) – (0.100 * Age) + (0.484 * Height in cm) + (0.164 * Body weight) – (0.038 * Resistance). The percentage of accurate predictions of the new equation was low, at 34%, but compared to the current equations this was the highest percentage. The bias of the FFM with the new equation compared to ADP, was 0.3 ± 3.8 kg, and the mean absolute error was 3.1 ± 2.3 kg. This shows that the new equation can accurately measure FFM in groups, but per person the FMM can differ from the measured FFM by 3.1 kg. Conclusion: In conclusion, the newly developed Beijer_hva equation does not accurately estimate the FFM. For individual estimation of the FFM the Beijer_hva equation is not suitable, but the equation can be used for estimating FFM in groups of older adults (55+) with overweight and obesity.