Departamento de Nutrición y Bioquímica, Facultad de Ciencias, Pontificia Universidad Javeriana, Bogotá, DC, Colombia.
Growth, Exercise, Nutrition and Development (GENUD) Research Group, Universidad de Zaragoza, Zaragoza, Spain.
BMC Pediatr. 2022 Jan 22;22(1):58. doi: 10.1186/s12887-021-03041-z.
Lean / Fat Free Body Mass (LBM) is metabolically involved in active processes such as resting energy expenditure, glucose uptake, and myokine secretion. Nonetheless, its association with insulin sensitivity / resistance / glucose tolerance and metabolic syndrome remains unclear in childhood.
The current investigation aimed to examine the differences in fat-free mass /lean body mass according to the presence of insulin sensitivity/insulin resistance/glucose tolerance/metabolic syndrome in children. A systematic search was carried out in Medline/PubMed, Embase, Scopus, Web of Science, and SciELO, covering the period from each database's respective start to 21 June 2021. Two researchers evaluated 7111 studies according to the inclusion criteria: original human studies, written in English or Spanish, evaluating fat-free mass/lean body mass in children and adolescents including both with and without insulin sensitivity/insulin resistance /glucose tolerance and metabolic syndrome and reported the differences between them in terms of fat free mass/lean body mass. The results of the studies were combined with insulin sensitivity, insulin, resistance, glucose tolerance and metabolic syndrome. The standardized mean difference (SMD) in each study was calculated and combined using the random-effects model. Heterogeneity between studies was tested using the index of heterogeneity (I), leave-one-out sensitivity analyses were performed, and publication bias was assessed using the Egger and Begg tests.
Finally, 15 studies which compared groups defined according to different glucose homeostasis criteria or metabolic syndrome out of 103 eligible studies were included in this systematic review and 12 studies in the meta-analysis. Meta-analysis showed lower fat-free mass/lean body mass percentage in participants with insulin resistance/glucose tolerance/metabolic syndrome (SMD -0.47; 95% CI, - 0.62 to - 0.32) while in mass units (kg), higher values were found in the same group (SMD, 1.01; 95% CI, 0.43 to 1.60).
Our results identified lower values of fat-free mass/lean body mass (%) in children and adolescents with insulin resistance/glucose tolerance/metabolic syndrome and higher values of fat-free mass/lean body mass when these are expressed in kg. The evidence of the impact of lean mass on children's glucose homeostasis or metabolic syndrome is limited, so future studies research should focus on explaining the effect of fat-free mass/lean body mass on different metabolic outcomes. Moreover, it may be interesting to evaluate the quality (muscle density) or functional (muscle strength) outcomes in addition to both absolute (kg) and relative (%) values in future studies. The systematic review was prospectively registered at PROSPERO (registration number CRD42019124734; available at: http://www.crd.york.ac.uk/prospero [accessed: 05 April 2019]).
瘦体重（Lean/Fat Free Body Mass，LBM）在代谢方面参与了许多活跃的过程，例如静息能量消耗、葡萄糖摄取和肌因子分泌。尽管如此，其与胰岛素敏感性/抵抗/葡萄糖耐量和代谢综合征之间的关系在儿童中仍不清楚。
本研究旨在探讨儿童中存在胰岛素敏感性/抵抗/葡萄糖耐量/代谢综合征时，无脂体重/瘦体重的差异。对 Medline/PubMed、Embase、Scopus、Web of Science 和 SciELO 中的数据库进行了系统检索，检索时间为每个数据库各自开始至 2021 年 6 月 21 日。两名研究人员根据纳入标准评估了 7111 项研究：原始人类研究，用英语或西班牙语撰写，评估儿童和青少年的无脂体重/瘦体重，包括具有和不具有胰岛素敏感性/抵抗/葡萄糖耐量和代谢综合征的个体，并报告了他们在无脂体重/瘦体重方面的差异。使用随机效应模型计算并结合了每项研究的标准化均数差（SMD）。使用异质性指数（I）检验研究之间的异质性，进行单因素敏感性分析，并使用 Egger 和 Begg 检验评估发表偏倚。
最终，从 103 项合格研究中纳入了 15 项比较不同葡萄糖稳态标准或代谢综合征定义的组别的研究进行系统综述，12 项研究进行了荟萃分析。荟萃分析显示，胰岛素抵抗/葡萄糖耐量/代谢综合征组的无脂体重/瘦体重百分比较低（SMD -0.47；95%CI，-0.62 至-0.32），而在同一组中，无脂体重/瘦体重的单位（kg）值较高（SMD，1.01；95%CI，0.43 至 1.60）。
我们的研究结果发现，患有胰岛素抵抗/葡萄糖耐量/代谢综合征的儿童和青少年的无脂体重/瘦体重百分比较低，而以 kg 表示时，无脂体重/瘦体重的数值较高。关于瘦体重对儿童葡萄糖稳态或代谢综合征的影响的证据有限，因此未来的研究应重点研究无脂体重/瘦体重对不同代谢结果的影响。此外，未来的研究除了绝对（kg）和相对（%）值外，还可以评估无脂体重/瘦体重的质量（肌肉密度）或功能（肌肉力量）结果，这可能很有趣。系统评价已在 PROSPERO（注册号 CRD42019124734；可在：http://www.crd.york.ac.uk/prospero[访问日期：2019 年 4 月 5 日]）中进行了前瞻性注册。
