Body mass index (BMI) is widely recognized as an important indicator of physical health. However, the current BMI standard and guidelines primarily focus on children and general adults, neglecting the specific needs of the oldest old aged 80 years or older. To address this gap, this guideline aims to provide recommendations on the appropriate range of BMI and weight management for the oldest old in China, including age calculation, defining the appropriate BMI range, BMI measurement indicators, and weight management strategies. It is intended to be utilized by medical and health organizations at all levels, as well as medical and nursing service institutions, to evaluate the BMI and manage the weight of the oldest old population.

China; Oldest old; Body mass index; Appropriate range; Body weight management