Hi Sara. It’s meant to be a guide, as each person’s (calorie) needs varies depending on age, gender activity level etc. However, the link to the Greek Nutrition Guidelines that I have also included at the end of the post provides serving sizes. Adding the link here too: https://www.olivetomato.com/eat-like-greek-greek-dietary-guidelines-a-better-choice/
On a ketogenic diet, your entire body switches its fuel supply to run mostly on fat, burning fat 24-7. When insulin levels become very low, fat burning can increase dramatically. It becomes easier to access your fat stores to burn them off. This is great if you’re trying to lose weight, but there are also other less obvious benefits, such as less hunger and a steady supply of energy. This may help keep you alert and focused.