This study investigated the effects of varying lipid ratios on the anaerobic co-digestion of high-lipid food waste (FW) in a mesophilic anaerobic membrane bioreactor (AnMBR). At a lipid concentration of 5 %, optimal biogas production (3.84 L/L/d) and lipid removal efficiency (78 %) were achieved; however, increasing lipid concentrations resulted in significant accumulations of long-chain fatty acids (LCFAs) and volatile fatty acids (VFAs). Batch tests further demonstrated the impact of various types of LCFAs, with stearic acid showing the slowest microbial growth rate (0.033d-1), confirming its role in the accumulation of acetate-dominated VFAs, potentially limiting the methanogenesis process at elevated lipid levels. Furthermore, at 8 % lipid content, the downregulation of key LCFA degradation enzymes and dominance of hydrogenotrophic methanogens indicate adverse conditions. The importance of the intricate interplay between LCFA degradation kinetics and microbial community for the system efficiency are evidenced, offering insights for optimizing and managing high-lipidic wastes.