Assess BMI

BMI Measurements

BMI is a screening tool for overweight and obesity (see the following table). BMI is calculated as a person’s body weight (in kilograms) divided by the square of their height (in meters). 

BMI = weight (kg) / height (m)2

BMI is moderately to strongly associated with other measures that capture the amount, location, and distribution of body fat. BMI can be approximated using tables that are widely available online or can be determined with online calculators.

BMI is classified as follows:

There is a direct relationship between BMI and obesity-related complications, with morbidity increasing as BMI increases across populations. Social determinants, race, ethnicity, and age may modify the risk associated with a given BMI and clinical judgment should be used when interpreting BMI for a particular patient (ASMBS, 2025). 

BMI does not measure body fat directly and can both underestimate and overestimate adiposity (Rubino et al., 2025). Therefore, caution is needed when interpreting BMI for individual patients because it does not provide information about a person’s body composition or health (Rubino et al., 2025). For example, very muscular athletes may have a high BMI but a low level of body fat. Conversely, an inactive person may have a normal BMI but have a high level of body fat.

Furthermore, a person’s ethnicity affects weight-associated health risks. For instance, Asian American patients are considered to have obesity at a BMI of 27. Additionally, compared with non-Hispanic White adults of the same age and the same BMI, non-Hispanic Black adults had less adipose tissue whereas Mexican American adults had more adipose tissue (GSA, 2024; Heymsfield et al., 2016). Inconsistencies across races and ethnicities are also seen in the correlation of waist circumference to BMI (GSA, 2024; Garvey et al., 2016). Thus, BMI may be used as a screening tool, but a more thorough clinical assessment should be used as part of the individual evaluation (Rubino et al., 2025). 

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In 2023, the American Medical Association (AMA) released a policy that qualifies the use of BMI in clinical practice (Berg, 2023). This policy states that BMI has significant limitations, including that it does not directly measure body fat levels and that other factors confound the interpretation of BMI and its impact on morbidity and mortality. The policy notes that heterogeneity of body shape and composition across race and ethnic groups, sexes, genders, and age span should be considered when interpreting BMI data. It states that BMI should be measured along with other valid measures of risk, including but not limited to waist circumference, percent body fat, and genetic or metabolic factors. 

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