BACKGROUND:Obesity in young adults and adolescents is associated with chronic co-morbidities. This project investigated whether being overweight or obese is a risk factor for periodontitis in adolescents (13-17 years) and young adults (18-34 years). METHODS:A search of 12 databases was conducted using Medical Subject Headings/Index and Emtree terms. Based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses, articles published between 2003 and 2016 were screened that reported periodontal and anthropometric measures. The Newcastle-Ottawa Scale was used to appraise the quality of studies. RESULTS:Of 25 eligible studies from 12 countries, 17 showed an association between obesity and periodontitis (odds ratios ranged from 1.1 to 4.5). The obesity indicators of body mass index, waist circumference, waist-hip ratio and body fat percentage were significantly associated with measures of periodontitis of bleeding on probing, plaque index, probing depths, clinical attachment loss, calculus, oral hygiene index and community periodontal index. Two prospective cohort studies in the review showed no significant association between obesity and periodontitis, but these studies had limitations of study design and used inappropriate epidemiological diagnostic measures of periodontitis. CONCLUSION:There was evidence to suggest that obesity is associated with periodontitis in adolescents and young adults. Systematic Review Registration: PROSPERO Registration Number: CRD42016046507.