What is the constitutional authority for presidents to issue executive orders?

Annette suffers from recurrent episodes of gorging on large quantities of food followed bypurging through self-induced vomiting in order to prevent gaining weight. although her weight is well below normal to the point that others see her as "skin and bones," she worries excessively about being fat. she also has impulse control problems in other areas of her life. she is suffering from ) binge-eating/purging anorexia2) restrictive anorexia3) bulimia nervosa 4) binge-eating disorder