In the subgroup analysis that compared serum levels of IL-6 (pg/mL), five studies [34, 35, 40, 42, 43] showed that the baseline IL-6 levels of people with obesity and periodontitis (OP) were higher than those of normal-weight patients with periodontitis (NP) before treatment (MD = 0.51, CI = 0.09–0.93) (Figure S1). Here, IL6 is linked to obesity disorder.