Last update: 1.5.2017.
Diet could be defined as food and drink regularly consumed. It could also be defined as habitual nourishment. These definitions define diet as whatever you happen to eat.
Other definition of diet could be a regimen of eating and drinking sparingly so as to reduce one's weight. This would be the definition that means restricting calories to lose weight.
We do not classify diets with any of the above definitions. We look at diets as sets of rule by which nutrition is obtained. There is e.g. the vegetarian diet which avoids meats. Ketogenic diet avoids carbohydrates. Muslims have halal. Christians do not eat blood. Many times there are a lot of sub categories inside these diets and someone might even be offended by just talking about a vegetarian diet and not mentioning the variety of nuances there are.
We do not address belief based diets like Kosher diet.