Adipocyte–macrophage interaction in obesity can cause adipose tissue inflammation and contribute to insulin resistance. Here, we investigated the effect of SlimTrym®—a formulated product containing citrus polymethoxyflavones (PMFs), green tea extract, and lychee polyphenols—on 3T3-L1 adipocyte differentiation and obesity-induced inflammation. SlimTrym® inhibited mitotic clonal expansion (MCE) of 3T3-L1 adipocytes by inducing G1 cell cycle arrest via upregulation of p21 and p53. SlimTrym® attenuated adipogenic differentiation by downregulating adipogenic factors, such as CCAAT-enhancer-binding proteins (C/EBPs) and peroxisome proliferator-activated receptor γ (PPARγ), and upregulating AMP-activated protein kinase (AMPK). Pretreatment with compound C significantly reduced SlimTrym®-mediated suppression of lipid accumulation. SlimTrym® reduced the expression of pro-inflammatory cytokines, including monocyte chemoattractant protein 1 (MCP-1), interleukin (IL)-1β and IL-6, in co-cultured 3T3-L1 adipocytes and RAW264.7 macrophages. C57BL/6 mice administered with SlimTrym® for 16 weeks showed markedly reduced high-fat diet (HFD)-induced infiltration of monocytes/macrophages in adipose tissue; however, the level of M2 macrophage markers (CD163 and IL-10) was increased. Taken together, these findings indicate that SlimTrym® exerts both anti-adipogenic and anti-inflammatory effects, and can potentially treat obesity and adipose tissue inflammation.