Lumbar belts are one of the possible indication among therapeutic strategies for low back-pain management, but few studies and insufficient data have been reported to evaluate their clinical effects. Recently, a semi-analytical model has been developed for in-silico trials of lumbar belts on patients' morphologies (Molimard et al., 2019a), incorporating for the first time the trunk deformation and providing an estimation of the pressure applied on the trunk. A unique indicator of the belt mechanical efficiency was proposed: Pressure is integrated into a bending moment, calculated at the center of curvature in the lumbar region, characterizing the action of reducing lumbar spine lordosis. One important finding of this study indicates that patient BMI impacts belt efficacy, suggesting that overweight is predictive of decreased belt effectiveness. However, more morphologies in the high Body Mass Index (BMI) range were needed to confirm this trend, showing the importance of controlling the cohort characteristics. To investigate this association between belt efficacy and morphological indicators, 24 different morphologies were artificially generated using a Proper Orthogonal Decomposition (POD) from a base of 13 experimental trunk geometries, with most of them being overweight. They were used for a new in-silico clinical trial using one lumbar belt model and the waist-to-hip (WHR) ratio as a morphological indicator. The results confirmed our hypothesis showing that an increase in WHR is associated with a decrease in bending moment. In addition, no difference in these trends could be found between experimental and in-silico patients, nor between men and women.