Lower-Weight-Gain Phenotype Shows Greater Hypothalamic Proteomic Divergence from Control than Higher-Weight-Gain Phenotype in Cafeteria-Diet-Fed Rats

Cafeteria diet, rich in fat and sugar, rapidly induces metabolic dysfunction and alters central energy regulation. We examined behavior and hypothalamic protein abundance profiles in cafeteria-diet-fed rats classified into weight-gain quartiles (Q1–Q4) and compared with standard-chow-fed controls. Pre-adolescent male Sprague–Dawley rats (n = 39:10 controls; Q1–Q4, n = 7–8 each) received ad libitum access to standard chow or a palatable cafeteria diet and underwent open field testing followed by quantitative LC–MS/MS proteomics of the hypothalamus. Behavioral assessment showed no major differences in locomotion, anxiety-like parameters, or exploration, except for reduced grooming (p ≤ 0.05) in cafeteria-fed versus control animals. Global, threshold-independent analyses showed that the lower-weight-gain phenotype (Q1) was significantly more distant from controls than the higher-weight-gain phenotype (Q4) (multivariate distance to the control centroid; Mann–Whitney U, p = 0.006), a pattern also observed by principal component analysis and hierarchical clustering. Consistently, of 17 proteins that remained significant after false discovery rate correction, 16 differed between Q1 and control and only one between Q4 and control, despite both phenotypes having ad libitum access to the same cafeteria diet. These findings suggest that lower weight gain is associated with more extensive hypothalamic protein abundance changes, although a causal link remains to be established, and they highlight candidate pathways for future mechanistic studies.