Triponderal mass index rather than body mass index: An indicator of high adiposity in Italian children and adolescents.

OBJECTIVE: The aims of this study were to compare body mass index (BMI) and triponderal mass index (TMI) as predictors of fat mass percentage (FM%) and to develop TMI cutoffs for screening high adiposity. Therefore, TMI- and BMI-based references against FM% criterion for indicating adiposity in Italian children and adolescents were compared.

METHODS: This was a cross-sectional study conducted at the University of Rome Tor Vergata, Human Nutrition Unit, from 2008 to 2015. The sample included 485 children and adolescents from 8 to 17 y of age from central-southern Italy. Body weight (kg) and height (m) were assessed to calculate BMI and TMI. FM% was assessed by dual-energy x-ray absorptiometry. The prevalence of high adiposity was based on the 75th percentile of FM%, according to Ogden et al. curves. Statistical tests such as Mann-Whitney, Kruskal-Wallis, polynomial regression, receiver operating characteristics curve, and Cohen's κ, were performed using SPSS version 24 and MedCalc version 18.

RESULTS: Prevalence of high adiposity according to FM% was 50.2% (95% confidence interval [CI], 43.2-57.2) in boys and 43.2% (95% CI, 37.3-49.2) in girls. TMI rather than BMI could better predict FM% for both sexes (boys R2  = 0.67 and girls R2  = 0.79 versus boys R2  = 0.44 and girls R2  = 0.74, respectively). TMI was found to present a significantly higher area under the curve than BMI for indicating high adiposity in children and adolescents. TMI sex- and age-specific cutoffs were responsible by better classification of adiposity, followed by the International Obesity Task Force, World Health Organization, and Cacciari reference curves.

CONCLUSION: TMI is a useful screening tool in pediatric clinical practice and epidemiologic studies concerning childhood obesity.