There are many short term and long term health effects involved with following a crash diet, and the main health effect is yo-yo dieting. People embark on crash diets and cut off all food in a sudden manner. They surge back in a wave of hunger and start consuming a lot of food after the diet, gaining a lot of weight in this process. Seeing the weight gain, they'll start off on another crash diet to lose this weight and the cycle will continue. People who take up crash diets also experience depression, low energy, fatigue, misery and intense hunger.