Material and Method: Fifty-one healthy Thai adolescents (25 males and 26 females) aged 16 to 19 years volunteered in the present study. Underwater weighing (UWW) and dual energy X-ray absorptiometry (DEXA) were used for measurement of %BF for 2C and 3C models. UWW was also used for body density, DEXA for bone mineral content and protein content, and deuterium oxide dilution method for total body water (TBW), used in Lohman’s equation for 4C model.

Results: Body density, total body water, bone mineral density, and fat free mass were significantly higher in males than in females, whereas females had significantly higher fat than males (p<0.001). Compared to %BF4C, %BFUWW did not show significant deviations from the line of identity in males and females (R2 = 0.85 and 0.75 respectively), whereas %BFDEXA showed significant deviations from the line of identity in females (R2 = 0.59), but not in males (R2 = 0.60). Bland & Altman analysis demonstrated that UWW and DEXA tended to underestimate %BF in leaner adolescents and overestimate %BF in fatter adolescents.

Conclusion: Percent body fat using underwater weighing (2C model) may be used interchangeable with the 4C model in both genders. However, DEXA (3C model) can only be used in males and not in females, which require further research. A regression equation to relate 2C and 3C models to 4C was developed to enable a better estimation of percent body fat in Thai adolescents.

Keywords: Body fat assessment, 2C model, 3C model, 4C model, Dual energy X-ray absorptiometry (DEXA), Underwater weighing (UWW), Deuterium oxide dilution technique, Thais, adolescents