Diet specialization in naturopathy Crash diets are not dangerous for a healthy person unless they stick to them for a longer period of time, but the quick diet has disadvantages. Beware of nutritional deficiencies and the yo-yo effect. The one-sided diet in crash diets can lead to nutritional deficiencies because the body does not receive the nutrients it needs. If the person concerned returns to their old eating habits after the diet, the yo-yo effect also occurs: the pounds lost have returned to their hips and possibly more have been gained due to food cravings. The person concerned can counteract the yo-yo effect by exercising during the diet and rethinking their own diet. "If you want to maintain your new weight, you cannot avoid a permanent change in diet.