The Ketogenic diet is a pretty safe weight loss diet and you may experience some normal symptoms which means that your body is in Ketosis and is burning the body fat instead of your glucose.
When your body is in Ketosis you may experience some side effects that will feel like the flu symptoms and that's a good thing because it means the Ketogenic diet is working.
Side effects of the Ketogenic diet can include, Vomiting, Nausea, Weakness, Irritability, Constipation and Headaches.