What is a limitation of DXA when used for body fat measurement?

Dual-energy X-ray absorptiometry (DXA) is considered a highly effective tool for measuring body composition, including body fat percentage. However, one of its notable limitations is that it may not accommodate individuals with an extreme body mass index (BMI). DXA scans are typically designed for a certain range of body sizes, and when individuals fall significantly outside of this range—whether underweight or obese—accuracy and reliability of the measurements can be compromised.

The technology relies on the precision of x-ray attenuation to differentiate between lean mass and fat mass, and extreme sizes may lead to difficulties in obtaining clear and representative images. This limitation can result in an underestimation or overestimation of body fat content, particularly in cases of obesity where excess mass could interfere with the scanning process.

Considering the other options, while DXA may have limitations in pediatric populations and certain athletic considerations, these factors do not limit its functionality as severely as accommodating individuals with extreme BMI does. Moreover, fasting is not a prerequisite for undergoing a DXA scan, which distinguishes this method from others that may require fasting. Therefore, the correct answer illustrates a significant constraint in the application of DXA for body fat measurement in certain populations.