Going on an extreme diet, under the promise of losing weight in a week, is a risk factor for developing an eating disorder , such as anorexia or bulimia nervosa. Any diet that prohibits or suggests unlimited consumption of a particular food is not a healthy option. In most cases, since they are not designed by qualified professionals, they are not tailored to the individual's needs and characteristics and may be contraindicated if other health conditions exist or if the person is taking medication.