Diet quality of US adolescents during the transition to adulthood: changes and predictors1,2

Background: Influences on diet quality during the transition from adolescence to adulthood are understudied. Objective: This study examined association of 3 diet-quality indicators-Healthy Eating Index-2010 (HEI), Whole Plant Foods Density (WPF), and Empty Calories (EC; the percentage of calories from discretionary solid fat, added sugar and alcohol)-with lifestyle behaviors, baseline weight status, and sociodemographic characteristics in US emerging adults. Design: Data come from the first 4 waves (annual assessments) of the NEXT Plus Study, a population-based cohort of 10th graders enrolled in 2010 (n = 566). At each assessment, participants completed 3 nonconsecutive 24-h diet recalls, wore accelerometers for 7 d, and self-reported meal practices and sedentary behaviors. Self-reported sociodemographic characteristics were ascertained at baseline. Generalized estimating equations examined associations of time-varying diet quality with baseline weight status and sociodemographic characteristics and time-varying lifestyle behaviors. Results: Diet quality improved modestly from baseline (mean +/- SE: HEI, 44.07 +/- 0.53; WPF, 1.24 +/- 0.04; and EC, 35.66 +/- 0.55) to wave 4 for WPF (1.44 +/- 0.05, P < 0.001) and EC (33.47 +/- 0.52, P < 0.001), but not HEI (45.22 +/- 0.60). In longitudinal analyses, higher HEI and lower EC scores were observed in Hispanic compared with white participants. Better diet quality was associated with greater moderate-to-vigorous physical activity, more frequent breakfast and family meals, less frequent fast food and meals during television viewing, and shorter durations of television viewing, gaming, and online social networking. Diet-quality indicators were not consistently associated with time-varying physical inactivity, baseline weight status, or sociodemographic characteristics. Conclusions: Diet quality of emerging adults in the US remained suboptimal, but some aspects improved marginally over the 4-y study period. Meal contexts and sedentary behaviors may represent important intervention targets. There is substantial room for improvement in diet quality in all sociodemographic subgroups. This trial was registered at clinicaltrials. gov as NCT01031160.