This article explains how you can eat a low-carb diet, even if you are a vegetarian or vegan. Low-carb dieting doesn’t have to mean only protein and fat all the time.
The goal of this very low carb intake is to put the body in a state of ketosis, a situation where the body is forced to rely on "ketone bodies" for fuel. Ketosis occurs when the body is deprived of adequate carbohydrates, and this triggers the body to break down fat stores and release fatty acids into the blood. The liver converts fragments of the fatty acids into ketone bodies which are broken down to provide the body energy to survive. The ketogenic diet, or keto diet, has been around for almost 100 years.