INS and metabolic syndrome: The timeline map of keywords co-occurrence (Figure 6B) shows the differences in research hotspots of scholars in different periods: From 1992 to 2002, the high-frequency keywords are relatively more diverse, including “physical activity,” “exercise,” “body composition,” “insulin,” “insulin resistance,” “risk factor,” “prevention,” “BMI,” “leptin,” etc. From 2003 to 2011, the research focus shifted to “metabolic syndrome,” “intervention,” “prevalence,” “bariatric surgery,” “quality of life” and so on.