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

Abstract 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 R 2 = 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.