Aside from annoying my friends with constant tales of the benefits of a ketogenic diet , there were only two downsides I could think of. So in ketosis, you would expect a lipid profile normally considered healthier no matter how much fat was being consumed. That's only possible with food that has the highest possible calorie to weight ratio – which means eating essentially nothing but butter. Keto today replaces the carbs with fats rather than protein. Feeling fuller translates to willingly eating less, and in the end impressive weight loss.