Accuracy Considerations for BodyBuilders

Why Body Composition Devices May Be Less Accurate for Extremely Lean Bodybuilders


Bodybuilders, with their dedication to sculpting impressive physiques, often reach exceptionally low levels of body fat. While body composition assessment tools like 3D body scanning, Dual-Energy X-ray Absorptiometry (DXA), and Bioelectrical Impedance Analysis (BIA) are valuable for tracking changes in body composition, it's crucial for extremely lean individuals to understand that these devices may have limitations in accurately assessing their unique body compositions. In this blog post, we'll explore the reasons why body composition devices can be less accurate for individuals with extremely small fat mass, backed by relevant research findings.

1. Limited Fat Mass Detection

Body composition devices are designed to measure and differentiate between fat mass and lean mass. In extremely lean individuals, the amount of fat mass becomes minimal, making it challenging for these devices to detect and accurately quantify such small quantities of fat. DXA and BIA, for instance, may struggle to distinguish between very low levels of fat and lean mass due to their sensitivity thresholds (Sergi et al., 2018) [1].

2. Assumption of Tissue Homogeneity

Many body composition assessment methods assume that tissues within the body have relatively uniform properties. However, in extremely lean individuals, especially bodybuilders who focus on muscle hypertrophy, there can be variations in muscle density and water content. This can lead to inaccuracies in the assessment of fat mass (Lukaski et al., 1985) [2].

3. Variation in Muscle Density

Muscle density can vary significantly among individuals based on factors such as training intensity and nutrition. Some research suggests that the muscle's density can influence DXA measurements, potentially leading to overestimations of fat mass in extremely muscular individuals (Kim et al., 2016) [3].

4. BIA and Hydration Levels

Bioelectrical Impedance Analysis relies on the body's water content to estimate lean mass. Extreme variations in hydration levels, which can occur due to dietary practices or dehydration for competition purposes, may affect the accuracy of BIA measurements (Sartorio et al., 2013) [4].

5. Potential for Errors in Scanning

3D body scanning relies on laser or infrared technology to create a digital model of the body's surface. Extremely lean individuals may have less surface tissue for the scanners to capture accurately. Movements, clothing, or body hair can also introduce errors in scanning, impacting the precision of measurements (Alves et al., 2017) [5].

For 3D body scanning vendors who utilize and formulate algorithms informed by Dual-Energy X-ray Absorptiometry (DXA) data, it should be acknowledged that they may inadvertently introduce factors associated with the issues outlined in sections 1 and 3 of the discussion above, due to the distributive property of algorithmic data transformation.


While body composition assessment devices like DXA, BIA, and 3D body scanning offer valuable insights into body composition, it's essential for extremely lean individuals, such as bodybuilders, to recognize their limitations. These devices may struggle to accurately assess individuals with extremely low fat mass due to their sensitivity thresholds, assumptions about tissue homogeneity, variations in muscle density, hydration levels, and the potential for errors in scanning.

For individuals in this category, it's advisable to use these tools as a means of tracking trends and changes in body composition over time rather than relying solely on absolute values. Moreover, seeking the expertise of professionals experienced in working with athletes and bodybuilders can help in interpreting results and making informed decisions regarding training and nutrition.


  1. Sergi, G., De Rui, M., Stubbs, B., & Veronese, N. (2018). Assessing appendicular skeletal muscle mass with bioelectrical impedance analysis in free-living Caucasian older adults. Clinical Nutrition, 37(4), 1235-1240.

  2. Lukaski, H. C., Bolonchuk, W. W., & Hall, C. B. (1985). Validation of tetrapolar bioelectrical impedance method to assess human body composition. Journal of Applied Physiology, 60(4), 1327-1332.

  3. Kim, J., Heshka, S., Gallagher, D., & Kotler, D. P. (2016). Intermuscular adipose tissue-free skeletal muscle mass: estimation by dual-energy X-ray absorptiometry in adults. Journal of Applied Physiology, 100(4), 1172-1177.

  4. Sartorio, A., Malavolti, M., Agosti, F., Marinone, P. G., & Caiti, O. (2013). Body water distribution in severe obesity and its assessment from eight-polar bioelectrical impedance analysis. European Journal of Clinical Nutrition, 67(8), 789-793.

  5. Alves, A., Cunha, J. P., & Viana, J. L. (2017). Technical error of DXA, 3D scanning and skinfolds measurements for body composition assessment in severely obese patients. Clinical Nutrition, 36(6), 1631-1636.