Your body uses fat to store as energy for later use. In this group of disorders, you are missing an enzyme that you need to efficiently break down certain types of fats when it needs it most, for example after a long period without food, or during periods of illness such as viral infections. These situations act as triggers for people with these disorders, and can cause episodes called metabolic crises, which have a rapid and severe onset. As well as not having enough energy, partially broken-down fats or ketones can build up in the body causing damage to the organs. Avoidance of such triggers is key in the management of these disorders. You will have an emergency regimen (or plan) in place with strict instructions that must be followed should you become unwell in order to prevent serious and/or life-threatening complications.