Endometrial cancer (EC) arises from a convergence of metabolic, endocrine, and inflammatory disturbances largely driven by excess adiposity and diet-induced biochemical reprogramming. This review synthesizes molecular evidence linking adipose-derived estrogen excess, insulin/IGF-1 activation of PI3K/AKT/mTOR and RAS/MAPK pathways, adipokine imbalance, and NF-κB-dependent inflammation to EC initiation and progression. Mechanistic studies demonstrate that aromatase-mediated estradiol production in hypertrophic adipose tissue activates proliferative estrogen receptor-dependent transcriptional programs, potentiated by alterations in chromatin remodeling. Hyperinsulinemia and IGF-1 signaling independently accelerate mitogenesis and inhibit apoptosis by reinforcing anabolic metabolism and suppressing key tumor-suppressive checkpoints. Obesity-associated shifts in adipokines, including increased leptin/JAK2-STAT3 activity and reduced adiponectin/AMPK signaling, further amplify epithelial-mesenchymal transition, chronic inflammation, and metabolic stress. Additional emerging pathways, including riboflavin/FAD-dependent redox regulation and Ca2+ signaling dysregulation, reveal metabolic vulnerabilities such as enhanced LSD1 activity, FSP1-mediated ferroptosis resistance, and IP3R-driven endoplasmic reticulum stress that may support precision-targeted interventions. Dietary exposures modulate these biochemical networks bidirectionally: sucrose-rich ultra-processed foods intensify insulin resistance and inflammation, whereas Mediterranean and plant-forward dietary patterns attenuate insulin/IGF-1 activity, reduce systemic inflammation, improve estrogen metabolism, and enrich phytochemicals, such as glucosinolate-derived isothiocyanates, with detoxifying and epigenetic effects. Integrating biochemical biomarkers, including insulin, IGF-1, leptin, adiponectin, hs-CRP, and estrogen metabolites, provides a systems-level framework for identifying individuals at elevated risk and guiding metabolic, nutritional, and lifestyle interventions. Overall, the biochemical architecture of EC underscores a central role for diet-modifiable metabolic and inflammatory pathways in carcinogenesis and survivorship, offering promising avenues for prevention and personalized metabolic health strategies.