Original Article

Development and Validation of a Simple Equation to Predict Fat-Free Mass in the Adult Population


Background: Estimating Fat-Free Mass (FFM) is an integral part of Body composition measurements, so obtaining an accurate estimation for evaluating FFM is critical for researchers and specialists. We aimed to develop and validate a simple equation for predicting FFM in the adult population.

Methods: Participants were 1996 adults (1085 men and 911 women), and 18 to 69 years old from Ahvaz City, southern Iran. They were randomly divided into the derivation (n=1396) and the validation (n=600) groups with no significant differences from Jan 2018 to Feb 2020. FFM was measured by Bioelectrical Impedance Analyzer (BIA) (InBody 770©; Biospace, Seoul, South Korea). Based on the demographic variables retrieved from the Derivation group, 8 FFM predictive equations were developed using multiple regression; finally, the most accurate model (using the coefficient of determination (R2)) was chosen and then validated on the Validation group for more evaluation.

Results: The best equation derived from demographic characteristics was: " FFM= 0.28 × Weight (kg) + 0.57×Height (cm)+7.35×Sex (M=1, F=0)+0.03×Age (years)-70.61"; where sex = 1 for male and 0 for female. R=0.94, R2=0.89, standard error of the estimate=4.04 kg.

Conclusion: Our developed and cross-validated anthropometric prediction equation for fat-free mass estimation using BIA attained a high coefficient of determination, a low standard error of the estimate, and the lowermost coefficient of variation. Predictive equations may be reliable and valuable alternative methods for the clinical evaluation of fat-free mass in the adult population.

1. Gary Whitlock, Sarah Lewington, Paul Sherliker, et al (2009). Body-mass index and cause-specific mortality in 900 000 adults: collaborative analyses of 57 prospective studies. The Lancet, 373:1083-1096.
2. Caballero B (2019). Humans against obesity: who will win? Advances in Nutrition, 10:S4-S9.
3. Organization WH (2013). Global action plan for the prevention and control of noncommunicable diseases 2013-2020. ed. World Health Organization.
4. Fosbøl MØ, Zerahn B (2015). Contemporary methods of body composition measurement. Clin Physiol Funct Imaging, 35:81-97.
5. Bosy-Westphal A, Jensen B, Braun W, Pourhassan M, Gallagher D, Müller M (2017). Quantification of whole-body and segmental skeletal muscle mass using phase-sensitive 8-electrode medical bioelectrical impedance devices. Eur J Clin Nutr, 71:1061-1067.
6. Heyward VH, Wagner DR (2004). Applied body composition assessment. ed. Human Kinetics.
7. Hurt RT, Ebbert JO, Croghan I, et al (2021). The Comparison of Segmental Multifrequency Bioelectrical Impedance Analysis and Dual‐Energy X‐ray Absorptiometry for Estimating Fat Free Mass and Percentage Body Fat in an Ambulatory Population. JPEN J Parenter Enteral Nutr, 45(6):1231-8.
8. McLester CN, Nickerson BS, Kliszczewicz BM, McLester JR (2020). Reliability and agreement of various InBody body composition analyzers as compared to dual-energy X-ray absorptiometry in healthy men and women. J Clin Densitom, 23:443-450.
9. Ling CH, de Craen AJ, Slagboom PE, et al (2011). Accuracy of direct segmental multi-frequency bioimpedance analysis in the assessment of total body and segmental body composition in middle-aged adult population. Clin Nutr, 30:610-615.
10. Diniz KGD, Vieira DA, Colosimo EA, et al (2021). Derivation and validation of a simple anthropometric equation to predict fat-free mass in patients with chronic hepatitis C. Clin Nutr, 40:1281-1288.
11. Itani L, Tannir H, El Masri D, Kreidieh D, El Ghoch M (2020). Development of an Easy-to-Use Prediction Equation for Body Fat Percentage Based on BMI in Overweight and Obese Lebanese Adults. Diagnostics, 10:728.
12. Lyra CO, Lima SCVC, Lima KC, Arrais RF, Pedrosa LFC (2012). Prediction equations for fat and fat-free body mass in adolescents, based on body circumferences. Ann Hum Biol, 39:275-280.
13. Lohman T, Roche AF, Martorell R (1988). Anthropometric standardization reference manual. ed. Champaign IL: Human Kinetics Books.
14. Organization WH (1995). Physical status: The use of and interpretation of anthropometry, Report of a WHO Expert Committee. ed. World Health Organization.
15. Verney J, Schwartz C, Amiche S, Pereira B, Thivel D (2015). Comparisons of a multi-frequency bioelectrical impedance analysis to the dual-energy X-ray absorptiometry scan in healthy young adults depending on their physical activity level. J Hum Kinet, 47:73.
16. Lawrence I, Lin K (1989). A concordance correlation coefficient to evaluate reproducibility. Biometrics, 255-268.
17. Bland JM, Altman DG (1986). Statistical methods for assessing agreement between two methods of clinical measurement. Lancet, 1:307-10.
18. Deurenberg P, Weststrate JA, Seidell JC (1991). Body mass index as a measure of body fatness: age-and sex-specific prediction formulas. Br J Nutr, 65:105-114.
19. Thomson R, Brinkworth GD, Buckley JD, Noakes M, Clifton PM (2007). Good agreement between bioelectrical impedance and dual-energy X-ray absorptiometry for estimating changes in body composition during weight loss in overweight young women. Clin Nutr, 26:771-777.
20. Costa RFD, Masset K, Silva AM, Cabral B, Dantas PMS (2021). Development and cross-validation of predictive equations for fat-free mass and lean soft tissue mass by bioelectrical impedance in Brazilian women. Eur J Clin Nutr, 76(2):288-296.
21. Kanellakis S, Skoufas E, Karaglani E, et al (2020). Development and validation of a bioelectrical impedance prediction equation estimating fat free mass in Greek - Caucasian adult population. Clin Nutr ESPEN, 36:166-170.
22. Sun SS, Chumlea WC, Heymsfield SB, et al (2003). Development of bioelectrical impedance analysis prediction equations for body composition with the use of a multicomponent model for use in epidemiologic surveys. Am J Clin Nutr, 77:331-340.
IssueVol 52 No 2 (2023) QRcode
SectionOriginal Article(s)
DOI https://doi.org/10.18502/ijph.v52i2.11892
Equations Estimate Fat-free mass Bioimpedance Body composition

Rights and permissions
Creative Commons License This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.
How to Cite
Saboor M, Samadani M, Zare Javid A, Kazemi P, Sharifat M, Bavi Behbahani H, Cheraghian B. Development and Validation of a Simple Equation to Predict Fat-Free Mass in the Adult Population. Iran J Public Health. 2023;52(2):389-398.