In the described anorexia nervosa case, the patient's BMI was less than which percentile?

• A. 50th percentile
• B. 25th percentile
• C. 5th percentile
• D. 95th percentile

Answer: (C)

In children and teens, BMI is interpreted relative to peers of the same age and sex. Anorexia nervosa involves significantly low body weight, which is defined by falling into the lowest end of the BMI-for-age distribution. The standard threshold most often used is below the fifth percentile for age and sex, meaning the BMI is lower than what would be expected for at least 95% of peers. That’s why this scenario points to a BMI below the fifth percentile as the correct reference.

If the BMI were around the 25th percentile, it would be low but not considered significantly underweight. The 50th percentile is around the median (normal range), and the 95th percentile would indicate overweight.