Obesity significantly increases Alzheimer's disease (AD) and dementia risk. Understanding the link between a high body mass index (BMI) and these conditions is crucial for effective management and prevention.We aimed to estimate the burden of AD and other dementias attributed to high BMI from 1990 to 2019 based on sex, age, and socio-demographic indicators (SDI) at global, regional, and national levels.We collected data on deaths, disability-adjusted life years (DALYs), age-standardized mortality rates (ASMR), and age-standardized DALY rates (ASDR) from the 2019 Global Burden of Disease study for AD and dementia attributed to high BMI. We explored the correlation between SDI levels and ASDR.In 2019, there were 198,476.2 deaths (95% UI: 32,695.4-593,366.4) and 3,159,912.4 DALYs (848,330.5-8,042,531) attributed to high BMI. Numbers of deaths, DALYs, ASMR, and ASDR increased since 1990. Females had higher deaths, ASMR, and ASDR than males. Mortality and DALYs rates increased with age. ASMR and ASDR increased across five SDI levels, with the highest rise in Low-middle SDI. High-income North America had the most deaths [30,993.9 (5,101.7-89,912.9)], while North Africa and the Middle East had the highest ASMR [4.61 (0.79-13.64)] and ASDR [72.56 (20.98-181.16)] in 2019.The burden of AD and other dementias attributed to high BMI increased since 1990 globally and is still heaviest in developed regions. Females accounted predominantly for the burden than males. Timely measures are needed to against high BMI.