Retroperitoneal Fat (n.). 1. (MeSH) Fatty tissue inside the ABDOMINAL CAVITY, including visceral fat and retroperitoneal fat. It is the most metabolically active fat in the body and easily accessible for LIPOLYSIS.Increased visceral fat is associated with metabolic complications of OBESITY.nalogical dictionary. Adipose Tissue, White, White Adipose Tissue, White Fat [Hyper.]. Abdominal Adipose Tissue, Abdominal Fat, Adipose Tissue, Abdominal, Fat, Abdominal [Hyper.]. Retroperitoneal Fat (n.) [MeSH] ↕.