Excess adiposity and early cardiometabolic risk markers among adolescents and young adults in 70 countries: a multi-country cross-sectional study

Background The recent Lancet Commission recommended moving beyond body mass index (BMI)-only assessment by confirming excess adiposity with waist-based measures or, where available, direct body fat assessment. However, global evidence on the prevalence, classification, and early cardiometabolic relevance of anthropometrically confirmed excess adiposity (hereafter excess adiposity) among adolescents and young adults remains limited. We conducted this study across 70 countries in six World Health Organization (WHO) regions. Methods In this cross-sectional study, we used nationally representative WHO STEPS data from 70 countries between 2010 and 2023. Excess adiposity was defined using a Lancet Commission-informed anthropometric framework incorporating BMI, waist circumference (WC), and waist-to-height ratio (WHtR). Random-effects meta-analysis estimated prevalence, and regression models examined associations with cardiometabolic risk markers. Findings Among 60,634 individuals aged 15–29 years, the prevalence of excess adiposity was 33.7% (95% CI 29.4–38.0), ranging from 19.1% in South-East Asia to 48.2% in the Eastern Mediterranean region. Notably, 15.7% of participants had waist-confirmed adiposity, defined by both high WC and WHtR ≥ 0.50, despite not meeting BMI criteria for obesity. Higher odds of excess adiposity were observed in upper-middle-income countries (OR 2.54, 95% CI 1.40–4.60), high-income countries (OR 5.92, 95% CI 3.23–10.8), and physically inactive participants (OR 1.21, 95% CI 1.14–1.29). Excess adiposity was also associated with higher odds of having at least one (OR 2.15, 95% CI 1.86–2.49) and multiple (OR 4.09, 95% CI 3.20–5.23) cardiometabolic risk markers. Interpretation This study found that nearly one-third of adolescents and young adults had excess adiposity. Notably, one in six participants had waist-confirmed adiposity despite not meeting BMI criteria for obesity, identifying a group with greater cardiometabolic risk burden that would be missed by BMI alone. These findings support the Lancet Commission's move beyond BMI-only assessment and highlight the need to include waist-based measures in surveillance and prevention strategies to identify adiposity-related cardiometabolic risk earlier.