In the world of weight-loss diets, low-carbohydrate, high-protein eating plans often grab attention. The Paleo, South Beach, and Atkins diets all fit into that category. They are sometimes referred to as ketogenic or "keto" diets. But a true ketogenic diet is different. Unlike other low-carb diets, which focus on protein, a keto plan centers on fat, which supplies as much as 90% of daily calories. And it's not the type of diet to try as an experiment.