Background: The global rise in obesity increasingly includes extreme forms, notably BMI ≥ 50 kg/m2, which present disproportionate health risks, especially among older adults. Despite this, most epidemiological research aggregates all obesity (BMI ≥ 30 kg/m2), potentially underestimating the burden of extreme obesity. Understanding trends in this subgroup is critical for targeted public health and clinical responses. Methods: We analyzed data from the English Longitudinal Study of Ageing (ELSA) across four waves (2004-2005 to 2016-2017). Data were analysed on the entire population and also for those aged ≥ 65 years. BMI was calculated from measured or self-reported height and weight and classified using WHO standards. Poisson regression with robust error variance was used to assess trends across BMI categories, adjusting for age and sex. Results: Extreme obesity (BMI 50-59.9 kg/m2) increased by 50% over the 12-year period, and for the first time, individuals with BMI ≥ 60 kg/m2 were observed in 2016-2017. Among older adults, mild obesity (BMI 30-39.9 kg/m2) declined slightly, while class II obesity (BMI 40-49.9 kg/m2) rose significantly. However, no individuals aged ≥ 65 years were recorded in the ≥ 60 kg/m2 category. Though absolute numbers remain small, the upward trend is clear and clinically significant. Conclusions: Extreme obesity is rising disproportionately, including among older adults, and requires urgent recognition as a distinct public health challenge. Healthcare systems must adapt to the complex needs of this population, including appropriate medical infrastructure, specialized care pathways, and enhanced clinical guidelines. Ongoing surveillance and tailored interventions are essential to address this growing burden.
