Linking pediatric obesity to youth-onset type 2 diabetes: integrated longitudinal and cross-sectional evidence from population-based studies worldwide.

Youth-onset type 2 diabetes mellitus (T2DM) is a rapidly growing pediatric metabolic disorder that parallels the global childhood obesity epidemic. Despite multiple population-based registries and a global meta-analysis documenting near-universal obesity at the time of a T2DM diagnosis, no integrated synthesis spanning 25 years and including diverse populations has been performed. Here we conducted a systematic review of PubMed and Scopus (January 2000 to March 2025) using longitudinal data from population-based registries in the USA (SEARCH), Canada (Manitoba), England and Wales (National Paediatric Diabetes Audit), Israel, Australia, and New Zealand as well as cross-sectional burden from a global meta-analysis (53 studies, n=8,942) and national audits. Study quality was appraised using the Newcastle-Ottawa Scale and A Measurement Tool to Assess Systematic Reviews v2. All registries showed a temporally parallel increase in the incidence of pediatric obesity and youth-onset T2DM. In the USA, the T2DM incidence rose 79% (3.8 → 6.8 per 100,000/yr, 2002-2018); in Manitoba, it nearly doubled (16.0 → 31.1 per 100,000/yr, 2009-2018); and Israel showed a 441% rise (0.63 → 3.41 per 100,000/yr, 2008-2019). The global pooled obesity prevalence at the T2DM diagnosis was 75.3% (95% confidence interval, 72.1%-78.5%), with approximately 41,600 new youth cases annually worldwide. Once-weekly semaglutide 2.4 mg (STEP TEENS trial) reduced the average body mass index by 16.1% at 68 weeks with concurrent glycemic improvement, while bariatric surgery achieved 95% T2DM remission at 3 years in adolescents (Teen-LABS cohort). Multicontinental evidence confirmed a robust temporally consistent obesity-T2DM link; obesity precedes T2DM at the population level and is present in approximately 75% of affected youths at diagnosis worldwide. Weight-reduction interventions, particularly glucagon-like peptide-1 receptor agonists and bariatric surgery, offer meaningful glycemic benefits; however, primary prevention of childhood obesity remains the most powerful strategy to arrest this epidemic.