Obesity is a multi-factorial metabolic disease for which safe, food-compatible interventions remain of interest. This narrative review evaluates the leaf-specific evidence for Eriobotrya japonica in obesity-related metabolic dysfunction and examines its bioactive constituents, extraction technologies, and combination research. Direct studies of loquat leaf preparations were distinguished from indirect evidence obtained with isolated compounds or other plant matrices. Preclinical studies indicate that loquat leaf extracts and triterpenoid-acid fractions can reduce lipid accumulation, body-weight gain, dyslipidemia, insulin resistance, and inflammatory markers in cell and rodent models; however, clinical evidence for obesity is not yet available. Loquat leaves contain triterpenic acids, flavonoids (including flavonols and flavan-3-ols), and phenolic acids, although reported contents vary with origin, harvest stage, and extraction method. Among the technologies reviewed, subcritical water extraction has direct leaf-specific evidence for concentrating corosolic and ursolic acids, whereas evidence for microwave- and enzyme-assisted extraction is less mature or concerns other compound classes. A 1:1 mixture of loquat- and lotus-leaf extracts produced stronger preclinical anti-obesity effects than either extract alone, but formal synergy was not tested; proposed combinations with curcumin or epigallocatechin-3-gallate remain hypotheses. Future work should standardize extracts, link composition to activity, test physical compatibility, and use factorial preclinical designs before clinical translation. Overall, loquat leaf is a promising but still preclinical resource for obesity-related metabolic dysfunction.

The global rise in obesity and associated metabolic disorders has fueled the demand for safe, multi-target therapeutics derived from natural sources. In this study, an artificial neural network combined with a genetic algorithm (ANN-GA), was employed to optimize the ultrasound-assisted extraction of loquat leaf extract (LLE). The optimal parameters—0.6% Tween 80, 328 W ultrasonic power, and 49 °C—enhanced extraction efficiency while minimizing energy consumption and surfactant use. In vitro, LLE exhibited potent dose-dependent inhibition of α-glucosidase (IC₅₀ = 3.75 μg/mL, 21.6-fold stronger than acarbose) and pancreatic lipase (IC₅₀ = 78.3 μg/mL), indicating strong inhibitory activity against these digestive enzymes. In high-fat diet-induced obese mice, LLE supplementation dose-dependently reduced body weight gain, serum total cholesterol, triglycerides, low-density lipoprotein cholesterol (LDL-C), and fasting blood glucose while elevating high-density lipoprotein cholesterol (HDL-C). In addition, LLE ameliorated liver injury (decreased ALT/AST) and oxidative stress (lowered MDA, increased SOD). These findings highlight LLE as a promising multi-target natural product for managing obesity and related metabolic disorders.