Chemical Characterization and Protective Effects of a Subcritical Water Extract from Olive Pomace Against Dyslipidemia and Hepatic Steatosis in High-Fat/High-Sugar Diet–Fed Mice

Olive pomace, a byproduct of olive oil production, is a rich source of bioactive phenolic compounds with potential health benefits. This study aimed to characterize the chemical composition and evaluate the metabolic effects of a subcritical water extract from California olive pomace (SWE COP) obtained from Arbequina olives. The extract was mainly composed of carbohydrates (72.81%) and contained 66.62 ± 1.22 mg gallic acid equivalents/g of phenolics, with 3,4-DHPEA-EDA, hydroxytyrosol, and verbascoside identified as the predominant compounds. Male C57BL/6N mice were fed a standard diet (SD; n = 7), a high-fat and high-sugar diet (HFSD; n = 7), which was used to induce features of diet-associated metabolic syndrome, or an HFSD supplemented with 3% (<i>w</i>/<i>w</i>) SWE COP (n = 7) for 16 weeks. Supplementation with SWE COP significantly reduced plasma triglycerides and increased HDL cholesterol levels compared with the HFSD group. Moreover, SWE COP improved glucose tolerance, enhanced insulin sensitivity, and reduced mesenteric and epididymal adiposity. Histological analysis showed that SWE COP alleviated hepatic steatosis and lowered the NAFLD activity score. These findings demonstrate that phenolic-rich SWE COP exerts beneficial effects on glucose and lipid metabolism and reduces liver fat accumulation in diet-induced obese mice. Overall, SWE COP represents a promising functional ingredient derived from olive industry byproducts for mitigating metabolic dysfunctions associated with obesity.