A fruitarian is an eater of fruits (fatty, sweet, and non-sweet) and green-leafed vegetables.
Too much hybridized sweet fruit will throw the body off balance. The fruitarian diet has to be done correctly (and I would recommend: only for a period of time, not indefinitely). Specifically, green-leafed vegetables must be eaten as they contain heavier minerals, calming properties, fiber and certain intangible items not available in fruits.
I do not personally recommend a long-term fruitarian diet, as it brings up the possibility of multiple types of nutritional deficiencies (demineralization and a lack of B vitamins) and potential neurological problems (especially those involving a lack of long-chain omega 3 fatty acids such as DHA and EPA). If one goes too long on a high-fruit diet, the first thing that will happen is that s/he will go deficient in salt (sodium), the next thing that will occur is a deficiency in calcium.