Laparoscopic sleeve gastrectomy (LSG), as an effective treatment for morbid obesity and its metabolic complications, exerts its therapeutic effects by significantly reducing body weight and improving metabolic disorders. Its core mechanisms involve multi-level regulation of free fatty acid (FFA) metabolism and chronic low-grade inflammatory states (represented by tumor necrosis factor-alpha, TNF-α). This paper systematically reviews the direct impact of LSG on FFA dynamics (including lipolysis, tissue uptake, and oxidation), as well as the molecular pathways through which it indirectly regulates TNF-α by reducing adipose tissue inflammation, improving intestinal barrier function, and modulating epigenetic modifications (such as SCD gene methylation). Postoperatively, FFA and TNF-α form a bidirectional promoting feedback loop. LSG effectively breaks this vicious cycle of mutual promotion between the two under obese conditions by reducing FFA levels and inhibiting TNF-α expression. Lower FFA levels alleviate inflammatory signal activation, while reduced TNF-α inhibits lipolysis, collectively promoting the restoration of insulin sensitivity. A thorough understanding of these mechanisms provides a theoretical basis for optimizing surgical strategies and developing targeted therapies.