Fats feature prominently in the culture, history and economics of the Disc. They appear from the microcosm of Sham Harga's fryers to the cosmic events of the Fifth Elephant. The mining or other extraction and distribution of fats and oils occupies large numbers of Humans and Dwarfs; they are a major resource.
In a society where electricity and petroleum are unknown, they provide light and lubrication as well as calories and other culinary benefits. Many Discworld residents (including Watch Commander Samuel Vimes), however, are endangered by their artery-clogging properties.