The company behind the diet, Forever Living, provides a list of people who should not try the Forever Living C9 diet. This list includes people with the following conditions: diabetes, heart disease, kidney disease, dementia, epilepsy, pregnancy or nursing.
Though the company does not mention this, no one with a history of disordered eating or a current eating disorder should try the diet.
Considering how strict the diet is and how little quality evidence is available to support it, most people are better off avoiding it.