In my experience, ketogenic diets tend to work because you're basically eating the same meals, just with one-third (the starch) cut out of it. If you're eating a traditional American meat-vegetable-potato dinner, eating just the meat and vegetables without the potatoes probably cuts out 500 calories. Regardless of any metabolic benefits, that calorie reduction makes quite a difference, and then if you factor in the better satiety and more stable blood-sugar levels that consuming fat and protein gives vs simple carbohydrates, you really wind up eating considerably less food, total.