Sarcopenic obesity and health outcomes: An umbrella review of systematic reviews with meta-analysis

Many studies support the idea that sarcopenic obesity (SO) could be considered a potential risk factor for negative health outcomes. These results have been inconsistent, and no umbrella reviews exist regarding this topic. Several databases until November 2023 were searched for systematic reviews with meta-analysis of observational studies (cross-sectional, case-control and prospective). For each association, random-effects summary effect sizes with correspondent 95% confidence intervals (CIs) were evaluated using the GRADE tool. Among the 213 papers initially screened, nine systematic reviews with meta-analysis were included, for a total of 384 710 participants. In cross-sectional and case-control studies, 30 different outcomes were analysed, and 18 were statistically significant. In any population addressed in cross-sectional and case-control studies, compared with non-SO, SO increased the prevalence of cognitive impairment (k = 3; odds ratio [OR] = 3.46; 95% CI: 2.24-5.32; high certainty of evidence), coronary artery disease (k = 2; OR = 2.48; 95% CI: 1.85-3.31) and dyslipidaemia (k = 3; OR = 2.50; 95% CI: 1.51-4.15). When compared with sarcopenia or obesity, the results were conflicting. In prospective studies, the association between SO-compared with non-SO-and other negative outcomes was supported by low/very low certainty of evidence and limited to a few conditions. Besides, no comparison with sarcopenia or obesity was provided. Finally, only a few studies have considered muscle function/physical performance in the diagnostic workup. SO could be considered a risk factor only for a few conditions, with the literature mainly based on cross-sectional and case-control studies. Future studies with clear definitions of SO are needed for quantifying the importance of SO-particularly when compared with the presence of only sarcopenia or obesity-and the weight of muscle function/physical performance in its definition.