The objectives of this study were to develop age- and sex-specific reference percentiles for fat mass index (FMI) and fat-free mass index (FFMI) in adolescents aged 14 to 19 years and to determine differences in overweight/obesity classification by FMI and body mass index (BMI). The EVA4YOU study is a single-center cross-sectional study conducted in western Austria. Cardiovascular risks including anthropometric measurements and bioelectrical impedance analysis were assessed in adolescents (mean age 17 years). FMI and FFMI were calculated as the ratio of fat mass (FM) and fat-free mass (FFM) to the square of height and compared to study population–specific BMI percentiles. One thousand four hundred twenty-two adolescents were included in the analysis. Girls had a significantly higher mean FM and FMI and a significantly lower mean FFM, FFMI (p < 0.001, each), and mean BMI (p = 0.020) than boys. Body composition classification by FMI and BMI percentiles shows a concordance for the < 75th and > 97th percentile, but a significant difference in percentile rank classifications between these two cut-off values (all p < 0.05). Based on FMI, 15.5% (221/1422) of the whole population and 29.4% (92/313) of those between the 75th and 97th percentiles are classified one category higher or lower than those assigned by BMI. Conclusion: Classification of normal or pathologic body composition based on BMI and FMI shows good accordance in the clearly normal or pathologic range. In an intermediate range, FMI reclassifies categories based on BMI in more than a quarter of adolescents. Cut-off values to differentiate normal from pathologic FMI values on a biological basis are needed.Trial registration: The study is registered at www.clinicaltrials.gov (Identifier: NCT04598685; Date of registration: October 22, 2020). What is Known:• Chronic non-communicable diseases (NCDs) are the leading cause of morbidity and mortality globally, with major risk factors including unhealthy diets, harmful behaviors, and obesity. Obesity in children and adolescents is a key risk factor for later NCDs, which is commonly measured by Body Mass Index (BMI).• BMI can be misleading as it doesn't distinguish between fat mass (FM) and fat-free mass (FFM), leading to potential misclassification of obesity in children. Previous studies have already suggested the use of the Fat Mass Index (FMI) and Fat-Free Mass Index (FFMI) as a more accurate measures of body composition. What is New:• This study adds the first age- and sex-specific reference values for FMI and FFMI in Austrian adolescents using bioelectrical impedance analysis (BIA) as a safe and secure measurement method of a large representative cohort.• We found percentile misclassification between BMI and FMI when categorizing for obesity, especially in intermediate categories of body composition. Furthermore, when comparing the new reference values for FMI and FFMI to existing ones from the US, UK, and Germany we could show a good alignment within the European cohorts and major differences with American values, indicating and confirming the difference of FMI and FFMI for different populations of different ethnical background, living on different continents.

Aim: To assess the impact of maternal, neonatal, and adolescent factors on the development of non-alcoholic fatty liver disease (NAFLD) in a cohort of 14- to 19-year-old adolescents. Methods: This study is part of the Early Vascular Ageing in the YOUth study, a single-center cross-sectional study conducted in western Austria. Maternal and neonatal factors were extracted from the mother-child booklet, adolescent factors were evaluated by a face-to-face interview, physical examination, and fasting blood analyses. Liver fat content was assessed by controlled attenuation parameter (CAP) using signals acquired by FibroScan ^® (Echosense, Paris, France). The association of maternal, neonatal, and adolescent factors with CAP values was analyzed using linear regression models. Results: In total, 595 adolescents (27.2% male) aged 17.0 ± 1.3 years were included. 4.9% (n = 29) showed manifest NAFLD with CAP values above the 90 ^th percentile. Male sex (p < 0.001), adolescent triglyceride levels (p = 0.021), Homeostatic Model Assessment for Insulin Resistance index and BMI z-score (p < 0.001, each) showed a significant association with liver fat content in the multivariable analysis. Maternal pre-pregnancy BMI was associated with CAP values after adjustment for sex, age, and birth weight for gestational age (p < 0.001), but this association was predominantly mediated by adolescent BMI (indirect effect b = 1.18, 95% CI [0.69, 1.77]). Conclusion: Components of the metabolic syndrome were the most important predictors of adolescent liver fat content. Therefore, prevention of NAFLD should focus on lifestyle modification in childhood and adolescence.

(1) Background: Unhealthy dietary behaviors are estimated to be one of the leading causes of death globally and are often shaped at a young age. Here, we investigated adolescent diet quality and its predictors, including nutrition knowledge, in two large Central European cohorts. (2) Methods: In 3056 participants of the EVA-Tyrol and EVA4YOU prospective population-based cohort studies aged 14 to 19 years, diet quality was assessed using the AHEI-2010 and DASH scores, and nutrition knowledge was assessed using the questionnaire from Turconi et al. Associations were examined utilizing multivariable linear regression. (3) Results: The mean overall AHEI-2010 score was 42%, and the DASH score was 45%. Female participants (60.6%) had a significantly higher diet quality according to the AHEI-2010 and DASH score. AHEI-2010 and DASH scores were significantly associated (p < 0.001) with sex, school type, smoking, and total daily energy intake. The DASH score was additionally significantly associated (p < 0.001) with age, socioeconomic status, and physical activity. Participants with better nutrition knowledge were more likely to be older, to attend a general high school, to live in a high-income household, to be non-smokers, and to have a higher diet quality according to the AHEI-2010 and DASH score. (4) Conclusions: Predictors of better diet quality included female sex, physical activity, educational level, and nutrition knowledge. These results may aid focused interventions to improve diet quality in adolescents.

Aim: To determine the prevalence of metabolic dysfunction-associated steatotic liver disease (MASLD) among Western Austrian adolescents and its association with arterial stiffness as a marker of early vascular ageing. Methods: In the cross-sectional Early Vascular Ageing in the YOUth study, liver fat content was assessed by controlled attenuation parameter (CAP) using signals acquired by FibroScan (Echosense, Paris, France) in 14- to 19-year-old Austrian adolescents. Arterial stiffness was determined by carotid-femoral pulse wave velocity (cfPWV) and cardiovascular risk factors by a face-to-face interview, physical examination, and fasting blood analyses. Linear regression models and one-way analysis of variance were performed to analyze the association between liver fat content, MASLD and cfPWV. Results: A total of 1292 study participants (65.2% female) aged 17.2 ± 1.3 years were included. MASLD was detected in 62 (4.8%) adolescents. CAP value showed a significant association with cfPWV in the unadjusted model (p < 0.001) but lost its significant influence in the multivariable model after adjusting for sex, age and cardiovascular risk criteria (increased BMI or waist circumference, impaired glucose metabolism, elevated blood pressure, elevated plasma triglycerides, and decreased HDL cholesterol; p = 0.540). In the analysis of variance, a significant increase in cfPWV was observed in adolescents with any of the five cardiovascular risk criteria for MASLD (p < 0.001), but not with the additional presence of steatotic liver disease (p = 0.291). Conclusion: In our adolescent cohort, liver fat content and MASLD were not found to be independent predictors for early vascular ageing. Nevertheless, the determination of liver fat content can be a useful tool to identify adolescents at high risk for cardiovascular disease and metabolic syndrome.

Objectives: Systemic low-grade inflammation is associated with steatohepatitis in adults. We aim to explore if systemic low-grade inflammation, measured by plasma high-sensitivity C-reactive protein (hs-CRP), is also linked to steatotic liver disease in adolescents. Methods: In the cross-sectional Early Vascular Ageing in the YOUth study, systemic low-grade inflammation was measured by hs-CRP and liver fat content was quantified by the controlled attenuation parameters (CAP) derived from FibroScan^® (Echosense, Paris, France) measurements in 14- to 19-year-old Austrian adolescents. Cardiovascular risk factors and anthropometric data were collected through face-to-face interviews, physical examinations, and comprehensive fasting blood analyses. Linear regression models were performed to analyze the association between hs-CRP and CAP values. Results: A total of 1300 adolescents (64.6% female) with a mean age of 17.2 ± 1.3 years were included in this analysis. hs-CRP was significantly associated with CAP values in the simple linear regression model (b = 1.35, p = 0.044) and after adjustment for sex and age (b = 1.84, p = 0.006), suggesting an increase in systemic low-grade inflammation with increasing liver fat content. However, further adjustment for major factors of the metabolic syndrome (Homeostatic Model Assessment for Insulin Resistance, non-high-density lipoprotein cholesterol, body mass index z-score, systolic blood pressure z-score) led to a loss of significance of the mentioned association (b = −0.55, p = 0.419). Conclusions: Systemic low-grade inflammation measured by hs-CRP is linked to higher liver fat content in our adolescent cohort. However, this association is largely driven by components of the metabolic syndrome and the overall metabolic milieu, rather than reflecting liver-specific inflammation.

The presence of cardiovascular risk factors (CV-RFs) like obesity in adolescents leads to accelerated vascular ageing and a higher risk of cardiovascular disease (CVD) later in life. While Body Mass Index (BMI) is commonly used to assess adiposity, it lacks the ability to differentiate fat from lean mass. The Fat Mass Index (FMI) provides a more specific measure of adiposity and may better reflect cardiovascular risk. This study investigates the association between FMI percentiles and CV-RFs in adolescents, aiming to identify potential FMI thresholds indicative of elevated vascular risk. This analysis is part of the EVA4YOU study involving 1517 adolescents (14-19 years) from Tyrol, Austria. Triglycerides (TG), HDL cholesterol (HDL-C), LDL cholesterol (LDL-C), blood pressure (BP), and liver fat were classified as acceptable versus borderline or high. Diagnostic odds ratios (DORs) and prevalence of CV-RFs were assessed across FMI percentiles. Only 27.9 % of participants had no CV-RFs, while 12.4 % had ≥3. With rising FMI percentiles, CV-RFs became increasingly prevalent: only 9.5 % of adolescents above the 95th percentile had no CV-RFs, while 44.6 % had ≥3. DORs for high BP, TG, liver fat, and low HDL-C consistently increased with higher FMI percentiles. The prevalence of CV-RFs in adolescents is high and constantly increases with increasing FMI percentiles, showing a peak at the 95th percentile. However, since even lower FMI Percentiles are associated with increased odds of elevated CV-RFs, further diagnostics and preventive measures should not be based solely on a single percentile threshold. NCT04598685.