Comparison of anthropometric indicators as predictors of the percentage of fat mass in young people and older adults in Chile

Objective: To verify whether tri-ponderal mass index (TMI) has a higher accuracy than body mass index (BMI), waist circumference (WC) and waist-to-height ratio (WHtR) as predictors of obesity in young people and older adults in a region of Chile. Material and methods: A cross-sectional descriptive study was carried out in 1,176 adult subjects (565 men and 611 women) from the Maule region (Chile). The age range was from 20 to 80 years old. The percentage of fat mass (%FM) was evaluated by means of dual energy X-ray absorptiometry (DXA). Weight, height and WC were evaluated. TMI, BMI and WHtR were calculated. Results: The predictions of %FM for BMI were 0.47% for men and 0.50% for women, for TMI it was 0.50% for men and 0.51% for women, for WC it was 0.28% for men and 0.21% for women, and finally, for the WHtR it was 0.28% in men and 0.21% in women. The area under the curve (AUC) for the BMI was 0.85 in both men and women, for the TMI, it was 0.87 in men and 0.86 in women, for the WHtR, in men it was 0.76 and in women it was 0.72, and for WC, the AUC in men was 0.72 and in women it was 0.71. Conclusion: It was shown that TMI is the indicator that presented the greatest association with %FM and estimates body fat levels with greater precision than BMI, WC and WHtR. The results suggest its use and application as an indicator that discriminates obesity in young, middle and late-aged adults.