Crash diet is when u eat nothing until u get your desired weight.
i think it s telogen effluvium cuz i read it somewhere.By the way,after crash diet,some people gain their weight back. As soon as you stop the diet all your kilograms return. This happens because the metabolism in your organism has changed and your body got used to not receiving enough calories and therefore burnt lesser amount of them.Anorexia,bulimia ,kidney or liver failure,sudden death are some complications u can get from it