Preliminary assessment of sarcopenic obesity risk after sleeve gastrectomy using dual-modality imaging: a six-month MRI and DXA pilot study in women

Introduction Sarcopenic obesity (SO) is characterized by excess adiposity combined with skeletal muscle loss, but the absence of standardized diagnostic criteria makes interpretation of muscle tissue changes after bariatric surgery difficult, and different diagnostic indices can yield markedly different conclusions about the same patients. Methods This preliminary analysis from the SarxOb trial (NCT04617392) compared several body-composition indices for detecting SO risk in eleven female patients undergoing laparoscopic sleeve gastrectomy, prospectively followed for six months using dual-modality imaging — magnetic resonance imaging (MRI) and dual-energy X-ray absorptiometry (DXA). Results Lean body mass (LBM) decreased significantly from 56.3 ± 6.2 kg to 47.6 ± 6.0 kg (p < 0.001), while LBM as a percentage of total body weight increased from 50.4 ± 3.2% to 57.9 ± 4.3% (p = 0.003), reflecting a disproportionately greater loss of fat mass than lean mass. Appendicular skeletal muscle mass (ASM) decreased from 24.5 ± 3.3 kg to 20.1 ± 2.9 kg (p < 0.001). Critically, the choice of diagnostic index changed the apparent prevalence of SO risk entirely: by the ASM and ASM/height 2 indices, no patient met criteria for SO risk at any timepoint, whereas by the weight-adjusted ASM/weight index recommended by the 2022 ESPEN/EASO consensus statement, ten of eleven patients met SO-risk criteria at baseline and at one month postoperatively, decreasing to four of eleven by six months. MRI-based quantification of the right lower limb corroborated the DXA findings, showing a parallel increase in the muscle-to-adipose tissue ratio. Conclusion These results indicate that weight-adjusted indices detect a substantially higher burden of SO risk than traditional height-adjusted indices in this population, and that the choice of diagnostic index, not only the imaging modality used, is a major source of disagreement in reported SO risk prevalence after bariatric surgery. Given the small sample size inherent to this interim analysis of an ongoing trial, these findings should be considered exploratory and hypothesis-generating rather than confirmatory. As functional muscle assessment was not available in this interim report, these findings should be interpreted as SO risk by body-composition criteria rather than a complete EWGSOP2/ESPEN-EASO diagnosis.