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Why can muscular athletes have a high BMI without having excess body fat?

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Close-up of hands using a measuring tape to measure the waist circumference of an obese man wearing a white shirt and beige pants. — obesity The excessive accumulation of body fat can cause serious medical conditions.

Muscular athletes can have a high Body Mass Index (BMI) without having excess body fat because BMI is not a direct measure of body fat; rather, it is a calculation based solely on weight and height.123

The formula for BMI is:
$weight (kg) / [height (m)]^{2} = BMI$

Because this formula does not account for body composition, it cannot distinguish between weight derived from fat and weight derived from lean tissue. Muscle and bone are significantly denser than fat. Consequently, individuals with high muscle mass and low body fat—such as athletes—may have a high total body weight that results in a BMI classification of "overweight" or "obese," even though they do not possess the excess body fat typically associated with those clinical designations.14

Due to these limitations, many health professionals now recognize that BMI should not be used as the sole indicator of a patient's health or body fat levels.4