> _The Mathematics of Weight Loss | Ruben Meerman | TEDxQUT (Edited Version)_. Directed by TEDx Talks, 2013. _YouTube_, [https://www.youtube.com/watch?v=vuIlsN32WaE](https://www.youtube.com/watch?v=vuIlsN32WaE). # Fat is mostly exhaled as carbon dioxide It is commonly thought that burning fat transforms it into energy. However, the principle of conservation of mass implies that said fat cannot magically disappear: it has to go somewhere. It turns out that, with a lot of simplification, fat is burned with dioxygen to produce carbon dioxide and water. More accurately, 84% carbon dioxide and 16% water. Thus, most of the fat you burn when you lose weight is exhaled as carbon dioxide.