Associations Between Cardiorespiratory Fitness and Metabolic Syndrome in Adolescents: A Systematic Review and Meta-Analysis.

Introduction: Low levels of cardiorespiratory fitness (CRF) are associated with a greater risk of metabolic syndrome (MetS) in adolescence. In this sense, it is important to verify the strength of this association and the certainty that this evidence can be recommended. Objective: The objective of this paper is to summarize, through a systematic review and meta-analysis, the evidence available to verify the association between CRF and MetS in adolescents. Methods: PubMed, Embase, CINAHL, SPORTDiscus, LILACS, and Web of Science were searched until 20 August 2024. The risk of bias in each study was assessed via the AXIS tool, and the certainty of the evidence was assessed via the GRADE system. For the meta-analysis, the odds ratio (OR) was calculated with a 95% confidence interval. Results: Nine studies (7077 participants), all with a low risk of bias, were included in the systematic review. There was a high certainty of evidence that adolescents with low CRF have significantly greater odds of developing MetS (OR = 3.63 [CI 95%, 2.54 to 5.20]). The odds increase for low vs. moderate (OR = 4.23 [CI 95%, 2.64 to 6.78]) and low vs. high (OR = 8.03 [CI 95%, 3.20 to 20.18]) CRF are considered separately. The effect does not change according to the type of test used to assess CRF (p = 0.51). Conclusions: There is high certainty of evidence that adolescents with low CRF levels have significantly greater odds of developing MetS; therefore, it is essential that intervention strategies be designed to increase CRF in this population.