Obesity is a worldwide health concern and a well recognized predictor of premature mortality associated with a state of chronic inflammation. The objective was to evaluate the effect of soy protein hydrolysates (SPH) produced from different soybean genotypes by alcalase (SAH) or simulated gastrointestinal digestion (SGIH) on lipid accumulation in 3T3-L1 adipocytes. The anti-inflammatory effect of SPH produced by alcalase on LPS-induced macrophage RAW 264.7 cell line was also investigated. SAH (100 lM) derived from soybean enriched in β-conglycinin (BC) (up to 47% total pro-tein) decreased lipid accumulation (33-37% inhibition) through downregulation of gene expression of lipoprotein lipase (LPL) and fatty acid synthase (FAS). SGIH (100 lM) inhibited lipid accumulation to a lesser extent (8-14% inhibition) through inhibition of LPL gene expression. SAH (5 lM) decreased the production of nitric oxide (NO) (18-35%) and prostaglandin E2 (PGE2) (47-71%) and the expression of inducible nitric oxide synthase (iNOS) (31-53%) and cycloxygenase-2 (COX-2) (30-52%). This is the first investigation showing that soy hydrolysates inhibit LPS-induced iNOS/ NO and COX-2/PGE2 pathways in macrophages. Soybeans enriched in BCs can provide hydrolysates that limit fat accumulation in fat cells and inflammatory pathways in vitro and therefore warrant further studies as a healthful food. © 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.