Another limitation of BMI is that it ignores where fat is stored in the body. Visceral fat accumulates around the internal organs and poses a far greater health risk than subcutaneous fat, which lies beneath the skin. Two individuals with the same BMI could have vastly different health risk levels depending on how their fat is distributed. This is particularly concerning because visceral fat is strongly linked to conditions such as heart disease, diabetes, and metabolic syndrome.
Additionally, BMI does not consider demographic factors such as age, sex, or ethnicity. As people age, they tend to lose muscle mass, making their BMI appear normal even if their body fat percentage is high. Women naturally have a higher body fat percentage than men at the same BMI, yet BMI does not adjust for these differences. Ethnic variations also play a role—research has shown that Asian populations tend to develop metabolic diseases at lower BMIs, while African American individuals often have greater muscle mass at the same BMI, leading to potential misclassification.
Because of these shortcomings, additional methods like body composition scanning (bioelectrical impedance analysis) provide a more accurate picture of health. In addition, waist-to-hip and waist-to-height ratios offer better insights into fat distribution and cardiovascular risk.
While BMI remains a widely used tool due to its simplicity, it should not be relied upon in isolation to assess an individual’s health.