In my opinion (based on general thought and knowledge) it is not good for your health to leave anything out from your diet suddenly, so I question the healthiness of this diet. Of course there might be some benefits too e.g. if you leave excess sugars out from your diet, but I don't believe in all or nothing-type of solutions. Besides, peoples metabolisms are different, some bodies need more carbs than other (for example depending on your lifestyle choices or the exercise types) where someone need more protein based meals. There should be some golden mean when choosing and declaring some eating habits or lifestyle choices healthy and "banning" some foods from healthy diet choices.. Not everything suits for everybody!