The weight of junk food: Smaller hippocampal, amygdala, and prefrontal volumes in adolescents-The Cogni-Action Project.

Most studies investigating diet-brain relationships in youth focus on single foods. Whether the joint consumption of multiple food groups is associated with neuroanatomy during adolescence remains largely unexplored, particularly outside high-income countries. In this cross-sectional study, 61 Chilean adolescents (11.6 ± 1.07 years; 42.6% girls) underwent T1-weighted MRI. Volumes of total gray matter, hippocampus, amygdala, and selected prefrontal regions were extracted. Dietary intake was assessed using the Global Food Quality Index questionnaire. Confounder-adjusted linear regressions examined individual food group-brain associations, with correction for multiple comparisons. Canonical correlation analysis (CCA) was used to identify multivariate food group-brain covariation with permutation-based inference. Univariate analyses showed a significant inverse association between pastry consumption and hippocampal volume (β = -0.402, 95% CI: -0.571 to -0.228, adjusted R² = 0.34). CCA identified one significant multivariate mode linking higher unhealthy food consumption to brain volumes (r = -0.70, p = .008). Pastries, fried foods, and soft drinks showed the strongest contributions, whereas the corresponding brain variate was characterized by smaller hippocampal, amygdala, and anterior cingulate/prefrontal volumes. In conclusion, higher consumption of unhealthy food groups is associated with smaller limbic-prefrontal volumes in adolescents. Although causality cannot be inferred from these cross-sectional data, these findings highlight adolescence as a critical window for diet-brain health research.